Transcutaneous power transmission and communication for implanted heart assist and other devices

ABSTRACT

A system includes an implantable pump system for assisting blood flow in a patient including at least one movable valve. The movable valve is in a normally open state when the moveable valve is not being powered and a drive system in operative connection with the moveable valve to move the moveable valve under power. The system further includes an energy transfer system to provide energy to the drive system. The energy transfer system includes an external system including a power source and an external coil and an internal system including an internal coil adapted to receive transcutaneous energy transmitted from the external coil. The internal system has at least a first state wherein energy transmission from the external coil is required to provide operational power to the drive system.

CROSS REFERENCE TO RELATED APPLICATION

This application claims benefit of U.S. Patent Application Ser. No.61/506,621, filed Jul. 11, 2011, the disclosure of which is incorporatedherein by reference.

BACKGROUND

The following information is provided to assist the reader to understandthe technology described below and certain environments in which suchtechnology can be used. The terms used herein are not intended to belimited to any particular narrow interpretation unless clearly statedotherwise in this document. References set forth herein may facilitateunderstanding of the technology or the background thereof. Thedisclosure of all references cited herein are incorporated by reference.

Increasingly, medical devices are being implanted within patients to,for example, treat and/or diagnose various conditions. Implanted medicaldevices can be used to improve the quality of life as well as to prolongor save lives. Applications for implanted medical devices include, butare not limited to, regulating heart rates, assisting in blood flow,controlling incontinence, helping in hearing, helping to restore controlof paralyzed organs and treating depression.

As used herein, the term “powered” refers generally to electricallypowered medical devices. As used herein, the term “implanted” refers toa medical device either partially or completely inserted into the bodyof a patient (for example, a human patient). Often, the implantedmedical device is completely or fully inserted into the body. In anumber of such devices in which power must be supplied from an externalsource, power is delivered to the device and/or communications aremaintained with the device via percutaneous wires that connect one ormore external systems with the implanted device.

Heart assist or blood flow assist devices have been fully implantedwithin patients to assist the heart in providing adequate blood flow forthe needs of the body. Typically, the normal heart provides 1.5 averagewatts of useful power, which equates to 1.5 joules per second of usefulblood work, to satisfy the body's metabolic needs. A severely impairedheart might provide half this power and a heart assist device may makeup the difference by providing, for example 0.75 watts of useful power.If the assist device is 15% efficient, it will require a minimum of 5watts of input power. Heart assist devices in clinical use today usewires that pierce the skin to provide power for the fully implantedassist device. However, use of such percutaneous wires results is asignificant risk of infection along the wire track.

In a number of other implanted medical devices in which power must beprovided from an external source, a transcutaneous energy transfersystem (TETS) is used to wirelessly provide power to the implantedmedical device. In a number of such systems, a secondary power coil isimplanted and is electrically connected to an implanted rechargeablebattery which powers the implanted medical device. A system controllerincluding a primary power coil and a battery is worn by the patientoutside of the body. The primary coil transmits energy/power viamagnetic force/induction from the external battery across the skin ofpatient to the secondary coil without requiring piercing of the skin.The external battery can, for example, be removable and rechargeable.Typically, transcutaneous energy transfer systems are used for energytransmission in relatively low power applications (for example, lessthan 1 watt).

Although it is desirable to develop transcutaneous energy transfersystems for use with implanted heart assist devices to, for example,obviate the risk associated with percutaneous wiring, a number ofsignificant problems persist. As described above, the power requirementsfor implanted heart assist devices are substantially higher than withmany other medical devices, complicating the use of transcutaneousenergy transfer systems. Moreover, in the case of continuous flow heartassist devices, loss of power carries a risk of death of up to 40%. Anumber of precautions, including, for example, use of a plurality ofredundant external battery packs, may be required for safety.

SUMMARY

In one aspect, a system includes an implantable pump system forassisting blood flow in a patient including at least one movable valve.The movable valve is in a normally open state when the moveable valve isnot being powered and a drive system in operative connection with themoveable valve to move the moveable valve under power. The systemfurther includes an energy transfer system to provide energy to thedrive system. The energy transfer system includes an external systemincluding a power source and an external coil and an internal systemincluding an internal coil adapted to receive transcutaneous energytransmitted from the external coil. The internal system has at least afirst state wherein energy transmission from the external coil isrequired to provide operational power to the drive system. The internalsystem may, for example, be inoperable to power the drive system to movethe moveable pump through one stroke without energy transmission fromthe external coil when the internal system is in the first state.

The internal system may, for example, include a first energy storagedevice in electrical connection with the internal coil and the drivesystem. Energy is provided to the drive system via the first energystorage system. In a number of embodiments, the first energy storagesystem includes no battery. The first energy storage system may, forexample, include a capacitor system (which, for example, includes one ormore capacitors). In a number of embodiments, the first energy storageis capable of storing no more than 260 Joules (J) of energy, no morethan 130 J, 13 J, 6.5 J or even 1 J.

The external system may, for example, include an external control systemin operative connection with the power source and the external coil. Theinternal system may, for example, include an internal control system inoperative connection with the first energy storage system and theinternal coil. The external system may further include an externalcommunication system in operative connection with the external controlsystem. The internal system may further include an internalcommunication system in operative connection with the internal controlsystem.

In a number of embodiments, the internal communication system is adaptedto wirelessly transmit a signal to the external communication system toprovide information related to a voltage of the first energy storagesystem. The external system may, for example, be adapted to cause thepower source to energize the external coil upon receiving informationtransmitted from the internal communication system indicating that thevoltage is at least as low as a lower threshold value to charge thefirst energy storage system and to de-energize the external coil uponreceiving information transmitted from the internal communication systemindicating that the voltage is at least as high as a higher thresholdvalue.

In a number of embodiments, the external control system is adapted tocause the power source to energize the external coil after a determinedmaximum time period that the external coil has not been energizedregardless of whether or not the voltage is at least as low the lowerthreshold value. The external control system may, for example, beadapted to cause the power source to energize the external coil in amanner to result in the voltage being greater than the higher thresholdvalue in anticipation of a required high energy load.

In a number of embodiments, when the external coil is energized, energyis transmitted from the external coil to the internal coil over a rangeof frequencies. Energy may, for example, be transmitted from theexternal coil to the internal coil in a range of frequencies undercontrol of a spread spectrum algorithm. The nominal transmissionfrequency may, for example, be between 50 and 500 kHz. In a number ofembodiments, the range of frequencies extends from approximately 120 kHzto approximately 130 kHz. In a number of embodiments, the range offrequencies extends from approximately 120 kHz to approximately 126 kHz.

The external system and the internal system may, for example, be adaptedsuch that a change of frequency of energy transmitted from the externalcoil to the internal coil of +/−10% results in a change in transferefficiency of no greater than 10%. The external system and the internalsystem may, for example, be adapted to operate as a band-pass filter. Ina number of embodiments, tuning capacitors and leakage inductances formseries elements of the band-pass filter and magnetizing inductance formsa shunt element. Fixed tuning capacitors may, for example, be used. Theresonant frequency of at least one of the internal coil or the externalcoil may also be tunable. In a number of embodiments, the system has a Qfactor less than 10.

The spread spectrum algorithm may, for example, be a frequency hoppingspread spectrum algorithm. The spread spectrum algorithm may also be adirect sequence spread spectrum algorithm. In a number of embodiments,energy is transmitted from the external coil to the internal coil in therange of frequencies with a set resonant frequency of the external coiland a set resonant frequency of the internal coil.

In a number of embodiments wherein the external system includes anexternal communication system and the internal system includes andinternal communication system, the external communication is adapted totransmit to or receive informational signals from the internalcommunication system via at least one of an external radio or theexternal coil, and the internal communication system is adapted totransmit information signals to or receive signals from the externalcommunication system via at least one of an internal radio or theinternal coil. Information signals may, for example, be transmittedbetween the external coil and the internal coil within a frequency rangedifferent from a frequency range at which energy is transmitted from theexternal coil to the internal coil.

In a number of embodiments wherein the external system includes anexternal communication system and the internal system includes andinternal communication system, the internal communication system may,for example, be adapted to transmit a periodic status signal to confirmoperability of at least a portion of the internal system.

The system may further include a monitoring system to measure a variablerelated to current draw by the external coil to provide information tothe patient regarding position of the external coil relative to theinternal coil based at least in part on the measured variable related tocurrent draw on the external coil. The monitoring system may, forexample, include a current sensor in electrical connection with theexternal coil and in communicative connection with the external controlsystem.

In a number of embodiments, the internal system further includes asecond energy storage system. The internal system may have a secondstate wherein energy is drawn from the second energy storage system toprovide energy to the drive system. In a number of embodiments, thesecond energy storage system stores sufficient energy to provideoperation power to the drive system without transfer of energy from theexternal coil. The second energy storage system may, for example,include an internal rechargeable battery. In a number of embodiments,the internal system may be placed in the second state upon instructionalinformation being transmitted from the external control system via theexternal communication system to the internal control system via theinternal communication system. The external system may, for example, beadapted to allow the patient to manually cause the internal system to bein the second state. In a number of embodiments, no energy is drawn fromthe second energy storage system (for example, a rechargeable battery)to provide energy to the drive system in the first state. The secondenergy storage system (for example, a rechargeable battery) may, forexample, be adapted to power (or to provide operation power to) thedrive system for a period of time in the range of 5 minutes to 2 hours.

In a number of embodiments, the power source of the external systemconsists of a single rechargeable battery pack. The battery pack may,for example, include a plurality of lithium ion battery cells.

In a number of embodiments, the external coil is energized at a voltageof sufficient amplitude to provide an efficiency of at least 75%.

In a number of embodiments, the systems described above may, forexample, be used in connection with implanted blood flow assist systemsother than those including moveable valve pump systems and also withimplanted systems/devices other than blood flow (heart) assist systems.In that regard, in another aspect, a system includes an implantabledevice and an energy transfer system to provide energy to the drivesystem. The energy transfer system includes an external system includinga power source and an external coil. The energy transfer system furtherincludes an internal system including an internal coil adapted toreceive transcutaneous energy transmitted from the external coil. Theinternal system has at least a first state wherein energy transmissionfrom the external coil is required to provide operational power to theimplanted device (for example, to the drive system of an implanted bloodflow assist device). As described above, the internal system may furtherinclude a second energy storage system. The internal system may have asecond state wherein energy is drawn from the second energy storagesystem to provide energy to the implanted device. In a number ofembodiments, the second energy storage system stores sufficient energyto provide operation power to the implanted device without transfer ofenergy from the external coil. The second energy storage system may, forexample, include an internal rechargeable battery. In a number ofembodiments, the internal system may be placed in the second state uponinstructional information being transmitted from the external controlsystem via the external communication system to the internal controlsystem via the internal communication system. The external system may,for example, be adapted to allow the patient to manually cause theinternal system to be in the second state. In a number of embodiments,no energy is drawn from the second energy storage system (for example, arechargeable battery) in the first state. The second energy storagesystem (for example, a rechargeable battery) may, for example, beadapted to power (or to provide operation power to) the implanted devicefor a period of time in the range of 5 minutes to 2 hours (withoutreceiving energy from the external coil).

In another aspect, an energy transfer system includes a first systemincluding a power source, a first control system, and a first coil inoperative connection with the first control system. The system furtherincludes a second system including a second coil adapted to receivewireless energy transmitted from the first coil. When the first coil isenergized, energy is wirelessly transmitted from the first coil to thesecond coil over a range of frequencies under control of a spreadspectrum algorithm. The spread spectrum algorithm may, for example, be afrequency hopping spread spectrum algorithm. The spread spectrumalgorithm may, for example, be a direct sequence spread spectrumalgorithm. In a number of embodiments, the system has a Q factor lessthan 10.

In a number of embodiments, the first system and the second system areadapted such that a change of frequency of energy transmitted from thefirst coil to the second coil of +/−10% results in a change in transferefficiency of no greater than 10%. The first system and the secondsystem may, for example, be adapted to operate as a band-pass filter.Tuning capacitors and leakage inductances may, for example, form serieselements of the band-pass filter and magnetizing inductance may, forexample, forms a shunt element.

The system may for example, include fixed tuning capacitors. Theresonant frequency of at least one of the internal coil or the externalcoil may, for example, be tunable. Energy may, for example, betransmitted from the external coil to the internal coil in the range offrequencies with a set resonant frequency of the external coil and a setresonant frequency of the internal coil.

In a number of embodiments, the first coil is an external coil adaptedto be outside of a body and the second coil is an internal coil adaptedto be implanted within a body. The first coil is adapted totranscutaneously transmit energy to the second coil.

In a number of embodiments, the external coil is energized at a voltageof sufficient amplitude to provide an efficiency of at least 75%.

In a further aspect, a method of assisting blood flow in a patientincludes: placing an implantable pump system in fluid connection with ablood vessel, the implantable pump system including at least one movablevalve, the movable valve being in a normally open state when themoveable valve is not being powered, a drive system in operativeconnection with the moveable valve to move the moveable valve underpower; providing an external system including a power source and anexternal coil; providing an internal system including an internal coiladapted to receive transcutaneous energy transmitted from the externalcoil; and operating the internal system in a first state wherein energytransmission from the external coil is required to provide operationalpower to the drive system. Closing of the valve may also occur underpower in a forward stroke of the valve.

In another aspect, a method of powering a device includes: providing afirst system including a power source, a first control system, and afirst coil in operative connection with the first control system;providing a second system including a second coil adapted to receivewireless energy transmitted from the first coil, and wirelesslytransmitting energy from the first coil to the second coil over a rangeof frequencies under control of the spread spectrum algorithm. In anumber of embodiments wherein the first coil is an external coil placedoutside of a body and the second coil is an internal coil implantedwithin a body, the first coil is adapted to transcutaneously transmitenergy to the second coil.

In another aspect, a system for use in connection with an implantabledevice includes an external system including a power source, an externalcoil and an external control system including a first externalcontroller and a first external communication system in operativeconnection with the first external controller and with the externalcoil. The system further includes an internal system including aninternal coil adapted to receive transcutaneous energy transmitted fromthe external coil, an energy storage system such as a capacitor systemincluding at least one capacitor in electrical connection with theinternal coil and adapted to be placed in electrical connection with theimplantable device to provide energy to the implantable device, and aninternal control system including a first internal controller and afirst internal communication system in operative connection with thefirst internal controller and with the internal coil. The first internalcommunication system is adapted to wirelessly transmit a signal to thefirst external communication system to provide information related to avoltage of the capacitor system. The first external controller isadapted to energize the external coil upon receiving informationtransmitted from the first internal communication system that thevoltage is at a lower threshold value to charge the capacitor system andto de-energize the external coil upon receiving information transmittedfrom the first internal communication system that the voltage is at ahigher threshold value.

In a number of embodiments, the energy storage system/capacitor systemdoes not store sufficient energy to power the implantable device formore than one second without energizing (in real time) the first coil.In a number of embodiments, the external coil may be energized at avoltage of sufficient amplitude to provide an efficiency of at least 75%or an efficiency of at least 80%.

When the external coil is energized, energy may, for example, betransmitted from the external coil to the internal coil over a range offrequencies. Energy may, for example, be transmitted from the externalcoil to the internal coil in a range of frequencies via a spreadspectrum signal. In a number of embodiments, the range of frequenciesextends from approximately 120 kHz to approximately 130 kHz or fromapproximately 120 kHz to approximately 126 kHz.

The external system and the internal system may, for example, be adaptedsuch that a change of frequency of energy transmitted from the firstcoil to the second coil of +1-10% results in a change in transferefficiency of no greater than 10%. The external system and the internalsystem may, for example, be adapted to operate as a band-pass filter.Tuning capacitors and leakage inductances form series elements of theband-pass filter and magnetizing inductance may, for example, form ashunt element.

In a number of embodiments, the first internal communication system isadapted to transmit information including information related to thevoltage of the capacitor system via the internal coil and the externalcoil at a frequency outside of the range frequencies at which theexternal coil transmits energy to the internal coil and independently oftransmission of energy from the external coil to the internal coil.

The first internal communication system may also be adapted to transmita periodic supervisory signal or status signal to confirm operability ofat least a portion of the internal control system. The first internalcommunication system may, for example, include a radio frequencytransmitter to transmit information, and the first externalcommunication system may, for example, include a radio frequencyreceiver to receive information from the radio frequency transmitter. Ina number of embodiments, the radio frequency transmitter transmits at afrequency of approximately 13.56 MHz and the radio frequencyidentification receiver receives at a frequency of approximately 13.56MHz.

In a number of embodiments, the system further includes a system tomeasure a variable related to current draw by the external coil and asystem to provide information to the patient regarding position of theexternal coil relative to the internal coil based at least in part onthe measured variable related to current draw on the external coil. Thesystem to measure a variable related to current draw on the externalcoil may, for example, include a current sensor in electrical connectionwith the external coil and in communicative connection with the firstexternal controller.

In a number of embodiments, the internal control system further includesa second internal communication system, and the external control systemfurther includes a second external communication system. The secondinternal communication system may, for example, be adapted tocommunicate wirelessly and bi-directionally with the second externalcommunication system independently of the internal coil and the externalcoil. The second internal communication system may, for example,communicate with the second external communication system via radiofrequency energy of a different frequency from which the first internalcommunication system communicates with the second external communicationsystem. The frequency at which the second internal communication systemcommunicates with the second external communication system may, forexample, be in the range of approximately 402 MHz to approximately 405MHz.

In a number of embodiments, the internal control system further includesa second internal controller in operative connection with the implanteddevice and in communicative connection with the second internalcommunication system. At least one of the second internal communicationsystem and the second external control system may, for example, beadapted to communicate bi-directionally with another externalcommunication system. In a number of embodiments, the another externalcommunication system is adapted to provide information to a person otherthan the patient regarding at least one operational parameter of theimplanted device or at least one patient physiological parameter. Theinternal control system may, for example, be adapted to be programmed bythe person other than the patient to alter operation of the implanteddevice via communication from the another external communication system.

In another aspect, a method for operating a device implanted in apatient includes: positioning an external system including an externalcoil and an external control system comprising a first externalcontroller and a first external communication system in operativeconnection with the first external controller adjacent the patient;implanting within the patient an internal system including an internalcoil adapted to receive transcutaneous energy transmitted from theexternal coil, an internal energy storage system such as a capacitorsystem including at least one capacitor in electrical connection withthe internal coil and adapted to be placed in electrical connection withthe implantable device to provide energy to the implantable device, andan internal control system including a first internal controller and afirst internal communication system in operative connection with thefirst internal controller and with the internal coil; wirelesslytransmitting a signal from the first internal communication system tothe first external communication system to provide information relatedto a voltage of the capacitor system; energizing the external primarycoil upon receiving information transmitted from the first internalcommunication system that the voltage is at a lower threshold value tocharge the at least one capacitor; and de-energizing the externalprimary coil upon receiving information transmitted from the firstinternal communication system that the voltage is at a higher thresholdvalue.

In another aspect, a system for use in connection with an implanteddevice includes an external system including a power source, an externalcontrol system, and an external coil in operative connection with theexternal control system; and an internal system including an internalcoil adapted to receive transcutaneous energy transmitted from theexternal coil, wherein, when the external coil is energized, energy istranscutaneously transmitted to from the external coil to the internalcoil over a range of frequencies via a spread spectrum signal.

In a further aspect, a method of powering an implanted device includes:providing an external system including a power source, an externalcontrol system, and an external coil in operative connection with theexternal control system; providing an internal system including aninternal coil in connection with the implanted device and adapted toreceive transcutaneous energy transmitted from the external coil, andenergizing the external coil so that energy is transmitted from theexternal coil to the internal coil transcutaneously over a range offrequencies via a spread spectrum signal.

In another aspect, a system for use in connection with an implantabledevice includes an external system including a power source, an externalcoil and an external control system including a first externalcontroller and a first external communication system in operativeconnection with the first external controller and with the externalcoil. The system further includes an internal system including aninternal coil adapted to receive transcutaneous energy transmitted fromthe external coil, a first energy storage system such as a capacitorsystem including at least one capacitor in electrical connection withthe internal coil and adapted to be placed in electrical connection withthe implantable device to provide energy to the implantable device, andan internal control system including a first internal controller and afirst internal communication system in operative connection with thefirst internal controller and with the internal coil. The first internalcommunication system is adapted to wirelessly transmit a signal to thefirst external communication system to provide information related to avoltage of the capacitor system. The first external controller isadapted to energize the external coil upon receiving informationtransmitted from the first internal communication system that thevoltage is at a lower threshold value to transfer power from theexternal coil to the internal coil charge the capacitor system and tode-energize the external coil upon receiving information transmittedfrom the first internal communication system that the voltage is at ahigher threshold value. The first internal communication system isfurther adapted to transmit a periodic supervisory or status signal via,for example, the internal coils and the external coil to confirmoperability of the internal control system.

The system may further include a system to measure a variable related tocurrent draw on the external coil. The system to measure a variablerelated to current draw on the external coil may, for example, include acurrent sensor in electrical connection with the external coil and incommunicative connection with the first external controller.

In a number of embodiments, during initiation of power transfer from theexternal coil to the internal coil, the external control system isadapted to energize the external coil for a first period of time andmonitor for a signal from the internal system for a second period oftime. In a number of embodiments, the signal from the internal system isone of a signal transmitting information from the first internalcommunication system that the voltage is at the lower threshold value, asignal transmitting information from the first internal communicationsystem that the voltage is at the higher threshold value, or theperiodic supervisory signal. The external control system may, forexample, be adapted to de-energize the external coil if no signal isreceived within the second period of time for a defined delay period andenergize the external coil after the delay period. In a number ofembodiments, the first external controller is adapted to de-energize theexternal coil when the variable related to current draw on the externalcoil reaches a threshold value and re-energize the external coil toinitiate power transfer at a later time.

In another aspect, a system for use in connection with an implantabledevice includes an external system including a power source, an externalcoil and an external control system including a system to measure avariable related to current draw on the external coil. The systemfurther includes an internal system including an internal coil adaptedto receive transcutaneous energy transmitted from the external coil. Theexternal control system is adapted to de-energize the external coil uponwhen the variable related to current draw on the external coil reaches athreshold value.

In a further aspect, a system for use in connection with an implantabledevice includes an external system including a power source, an externalcoil and an external control system including a first externalcontroller and a first external communication system in operativeconnection with the first external controller and with the externalcoil. The system further includes an internal system including aninternal coil adapted to receive transcutaneous energy transmitted fromthe external coil to provide energy to the implantable device, and aninternal control system including a first internal controller and afirst internal communication system in operative connection with thefirst internal controller and with the internal coil. The first internalcommunication system is adapted to transmit information to the firstexternal communication to control energizing of the external coilindependently of and at a different frequency than a frequency at whichthe external coil is energized to transmit power to the internal coil.

In a further aspect, a system or energy transfer system includes a firstsystem including a power source, a first coil, and a first controlsystem. The first control system includes a first controller and a firstcommunication system. The first communication system is in operativeconnection with the first controller. The energy transfer system furtherincludes a second system adapted to be placed in electrical connectionwith a load and including a second coil, at least one energy storagedevice, and a second control system. The second control system includesa second controller and a second communication system. The secondcommunication system is in operative connection with the secondcontroller. The first system is adapted to wirelessly transfer energyvia the first coil to the second coil of the second system to, forexample, provide energy to the load. The second communication system isadapted to transmit a signal to the first communication system via thesecond coil to the first coil to provide information related to avoltage level of the at least one energy storage device. The firstcontroller is adapted to energize the first coil upon receivinginformation transmitted from the second communication system that thevoltage level is at a lower threshold value to charge the at least oneenergy storage device. The first controller is also adapted tode-energize the first coil upon receiving information transmitted fromthe second communication system that the voltage level is at a higherthreshold value.

In a number of embodiments, the at least one energy storage deviceadapted to provide energy to the load while the first coil isde-energized. In a number of embodiments, the at least one energystorage device does not contain sufficient energy to provide operationalpower to the load or to power the load for more than 20 seconds (or evenone second) without transmission of energy from the first system.

In a number of embodiments, the external coil is energized at a voltageof sufficient amplitude to provide an efficiency of at least 75% or toprovide an efficiency of at least 80%.

In a number of embodiments, the first system and the second system areadapted such that a change of frequency of energy transmitted from thefirst coil to the second coil of +/−10% results in a change in transferefficiency of no greater than 10%. The first system and the secondsystem may, for example, be adapted to operate as a band-pass filter. Ina number of embodiments, tuning capacitors and leakage inductances formseries elements of the band-pass filter and magnetizing inductance formsa shunt element. In an number of embodiments, when the first coil isenergized, energy is transmitted from the first coil to the second coilover a range of frequencies via a spread spectrum signal.

At least the second system may be internal to a body.

Energizing and de-energizing or on/off cycling of the first coil may,for example, be effected by On-Off keying or On-Off modulating the powertransmission frequency, enabling-disabling a primary driver for thefirst coil or enabling-disabling an H-bridge driver for the first coil.

In still a further aspect, an energy transfer system includes a firstsystem including a power source, a first control system, and a firstcoil in operative connection with the first control system; and a secondsystem including a second coil adapted to receive wireless energytransmitted from the first coil. When the first coil is energized,energy is wirelessly transmitted from the first coil to the second coilcovering a range of frequencies and produced by a spread spectrumsignal. The spread spectrum signal may, for example, be frequencyhopping spread spectrum. The spread spectrum signal may, for example, bedirect sequence spread spectrum. In a number of embodiments, the systemhas a Q factor less than 10.

The first system and the second system may, for example, be adapted suchthat a change of frequency of energy transmitted from the first coil tothe second coil of +/−10% results in a change in transfer efficiency ofno greater than 10%. In a number of embodiments, the first system andthe second system are adapted to operate as a band-pass filter. In anumber of embodiments, tuning capacitors and leakage inductances formseries elements of the band-pass filter and magnetizing inductance formsa shunt element.

The resonant frequency or the center frequency need not be changed ineffecting the spread spectrum signal. The system may thus include fixedtuning capacitors.

In a number of embodiments hereof, a fully implanted moving valve heartassist system derives its operational power in real time, during a firstoperational state, from an external power source (for example, viaTETS). The external power source may, for example, be provided by anon-redundant single source (for example, a single battery back). In anumber of embodiments, the system also includes an implantedrechargeable battery capable of operationally powering the moving valveheart assist device for a period of time when the system is in a secondoperational state, thereby temporarily eliminating TETS relatedelectromagnetic emissions and/or temporarily eliminating the need forexternally supplied TETS power.

The technology described herein, along with the attributes and attendantadvantages thereof, will best be appreciated and understood in view ofthe following detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an embodiment of a system hereof for transcutaneousenergy and data transmission.

FIG. 1B illustrates another embodiment of a system hereof fortranscutaneous energy and data transmission.

FIG. 2 illustrates a wearable article (for example, a vest) on a patientto support and position an external system such as the system of FIG. 1Aor 1B.

FIG. 3A illustrates a power control system of the system of FIG. 1A.

FIG. 3B illustrates an embodiment of a system in which datacommunication coils are positioned within the volume of power transfercoils.

FIG. 4A illustrates an example of a typical band-pass filter used tomodel the inductive coupling system.

FIG. 4B illustrates an equivalent circuit of a transformer wherein thetransformer has the structure of a band-pass filter, and whereincapacitors are added in series with the leakage inductances, X_(P) andX_(S).

FIG. 4C illustrates a simulation schematic for the inductive couplingsystem.

FIG. 4D illustrates a graph of simulation results demonstrating that thetransfer efficiency from Vin to Vout is good from 100 kHz to almost 300kHz.

FIG. 4E illustrates a simulated band-pass model of the inductivecoupling system.

FIG. 4F illustrates a graph showing agreement between the band-passmodel results and the transformer simulation results.

FIG. 4G illustrates another schematic model wherein, to ensure resonanceat 125 kHz, the capacitors were increased by a factor of four to keepthe same resonant frequency as FIG. 4C.

FIG. 4H illustrates a graph of simulation results showing a resonance at125 kHz, but wherein the bandwidth is comparatively narrow.

FIG. 5A illustrates a graph of efficiency as a function of output powerfor a range of output voltages.

FIG. 5B illustrates power requirements of the load (implanted device),external/primary AC output voltage and voltage of the internal/secondarycapacitor system as a function of time.

FIG. 5C illustrates a graph of efficiency as a function of the changefrom center frequency.

FIG. 5D illustrates efficiency as a function of duty cycle and outputpower as a function of duty cycle.

FIG. 5E illustrates power requirements of the load (implanted device),external/primary AC output voltage and voltage of the internal/secondarycapacitor system as a function of time.

FIG. 6 illustrates a schematic representation of the system of FIG. 1Aor 1B as part of an overall patient care system.

FIG. 7 illustrates use of the system such as the systems of FIG. 1A or1B in connection with an implanted blood flow assist system placed inline with the ascending aorta of a patient, wherein the system isillustrated schematically.

FIG. 8 illustrates an embodiment of an implantable, moving valve pumpsystem for use in connection with a system such as the systems of FIG.1A or 1B.

FIG. 9 illustrates schematically a portion of the system such as thesystems of FIG. 1A or 1B including a moving valve pump system.

FIG. 10A illustrates a perspective view of another embodiment of a valveassembly hereof including a closure member activating system to activelymove the closure members toward an open position or toward a closedposition.

FIG. 10B illustrates a perspective view of a section of the valveassembly of FIG. 10A.

FIG. 10C illustrates another perspective view of a section of the valveassembly of FIG. 10A wherein seals have been removed.

FIG. 10D illustrates a perspective view of the valve assembly of FIG.10A with the closure member thereof in an open position.

FIG. 11 illustrates a flow chart of an embodiment of a method ofoperation of the external system of FIG. 1B.

FIG. 12 illustrates a flow chart of an embodiment of a method ofoperation of the internal system of FIG. 1B.

DETAILED DESCRIPTION

As used herein and in the appended claims, the singular forms “a,” “an”,and “the” include plural references unless the content clearly indicatesotherwise. Thus, for example, reference to “a capacitor” includes aplurality of such capacitors and equivalents thereof known to thoseskilled in the art, and so forth, and reference to “the capacitor” is areference to one or more such capacitors and equivalents thereof knownto those skilled in the art, and so forth. Indication herein that oneelement, system or component is in connection with another element,system or component (for example, operative connection, electricalconnection, communicative connection etc.) includes either directconnection or indirect connection (for example, via one or moreintermediary elements or components) unless the content clearlyindicates otherwise.

In a number of representative embodiments hereof, a high-power energyand information transfer or communication system is used to power andbi-directionally communicate control and status information wirelessly(for example, transcutaneously or otherwise through body volume/mass)with one or more implanted medical devices. The system, for example,transfers power transcutaneously by electromagnetic induction from anexternally worn battery pack to the implanted device without the needfor percutaneous leads. In that regard, an external coil inductivelycouples power to an internal coil implanted beneath the skin. The energyand information transfer or communication systems hereof can also beused in connection with devices or systems other than implanted medicaldevices to wirelessly transfer energy.

In a number of embodiments, a system 10 as illustrated in FIG. 1A may,for example, be described as (at least in part) an inductively coupledDC-DC convertor. In FIG. 1A, a primary or external system 100 of system10 includes an external control system 105 including at least a firstexternal controller 110 (for example, a micro-controller ormicroprocessor). External system 100 further includes an external powersource 120 (for example, a single rechargeable battery pack), and anexternal coil 130 (often referred to as a primary coil). Coil powerdriver circuitry in electrical connection with external coil 130 can,for example, include an H-bridge inverter 140 to which control andtiming signals are provided by first external controller 110 (including,for example, control of pulse width modulation (PWM) duty cycle and/orswitching frequency). Secondary, internal or implanted system 200includes, for example, an implanted or internal coil 230 (often referredto as a secondary coil) and a control system 205 including one or morecontrollers, a rectifier 240, and power conditioning circuitry.

In the illustrated embodiment, internal control system 205 includes afirst internal controller 210, (for example, micro-controller orprocessor) which is adapted to, for example, control certain“housekeeping” control processes as further described below. Internalcontrol system 205 further includes a second internal controller 220 to,for example, control an implanted device 300. The functions of first andsecond controllers 210 and 220 can, for example, be combined in a singlecontrol system or distributed over more than two controllers.

In a number of embodiments, implanted device 300 is an implanted bloodflow assist pump including a motor 310 as, for example, described inU.S. patent application Ser. Nos. 13/370,113, 13/370,137 and 13/370,155and PCT International Patent Application No. PCT/US2012/024572, thedisclosures of which are incorporated herein by reference. One skilledin the art appreciates, however, that system 10 can be used inconnection with any implantable device for which power from an externalsystem is to be provided.

In a number of embodiments, system 10 compensates for coil alignment andcoupling variations between external coil 130 and internal coil 230 bydetecting and adjusting for changes in the system resonant frequency orcoupling efficiency. In a number of representative embodiments, whichwere not optimized, the system is able to deliver maximum output powerof approximately 35 watts at a coil separation or translationalmisalignment of up to 25 mm and rotational misalignment of 30 degrees,and operates at a maximum efficiency of, for example, 75%, 80% orhigher. Components of external system 100 can, for example, be supportedby or carried within a wearable article 400 such as a vest (see FIG. 2)that can also operate to align external coil 130 with internal coil 230.It is, for example, desirable to minimize orientational misalignment andto minimize a separation gap or distance between external coil 130 andinternal coil 230. In that regard, increasing misalignment and/orincreasing separation reduces coil coupling/power transfer efficiency.Many currently available transcutaneous energy transfer systems arequite sensitive to coil coupling effects caused by changes in alignmentand/or separation. Alignment and/or separation problems may, forexample, result from normal patient movement, and the system mustaccommodate patient-to-patient variations such as skin thickness andtension.

In general, changes in coil coupling result in changes in the resonantfrequency of the transcutaneous energy transfer system transformer orresult in system coupling losses, which can reduce power transfer andefficiency. In a number of embodiments, system 10 was designed toaddress the problem of changes in coil coupling by, for example, sensinga variable related to or dependent upon current draw, which increaseswith misalignment, on external coil 130 (for example, via a currentsensor 150 in electrical connection with coil 130). A system to provideinformation regarding the state of coil coupling to the patient may, forexample, be provided. For example, an indicator system 160 can beprovided on article 400 to notify the patient of alignment and/orseparation problems. Indicator system 160 may, for example, provideinformation to the patient in one or more manners adapted to be sensedby the patient (for example, audibly, visually, and/or tactilely).Indicator system 160 may, for example, include a series of visualindicators 162 a, 162 b, 162 c etc. (for example, red, yellow, and greenindicator lights) on article 400. Another indicator system 160′ can, forexample, provide information to the patient regarding the charge statusof battery pack 120 in a manner adapted to be sensed by the patient (forexample, audibly, visually, and/or tactilely). Indicator system 160′may, for example, include a series of visual indicators 162 a′, 162 b′,162 c′ etc. (for example, red, yellow, and green indicator lights) onarticle 400.

Another problem to be addressed by transcutaneous energy transfersystems is variation in the power demanded by implanted device 300. In anumber of embodiments hereof, compensation for variations in theelectrical load (that is, the power demanded by implanted device 300)occurs through a control protocol or methodology implemented betweenexternal system 100 and internal system 200 in which external coil 130is either energized (powered on) or de-energized (powered off) as afunction of the power demanded. System 10 is designed to accommodatevariations in load and power demand through a power control system,subsystem or circuitry (see, for example, FIG. 3A).

In a number of embodiments, internal system 200 has at least a firststate or first operational state in which implanted device 300 cannot beoperated in a typical, normal or clinically effective manner (that is,in a manner to achieve its intended purpose) without real-time transferof energy from external coil 130. In that regard, energy transmissionfrom external coil 130 is required in such embodiments to provideoperational power to the implanted device. In a number of embodiments,no energy from an internal battery (that is, a device in which chemicalenergy is converted to electrical energy) is supplied to implanteddevice when internal system 200 is in the first state. In general,rechargeable batteries have limited recharge cycles (for example,several hundred to a thousand) and thus may have a relatively limitedlife compared to other energy storage systems. In a number ofembodiments, an internal battery may be present in internal system 200,but it does not provide energy to implanted device 300 when internalsystem 200 is in the first state.

In the embodiment illustrated in, for example, FIGS. 1A and 3A, firstinternal controller 210 monitors a voltage or a variable related to ordependent upon the voltage on the output of implanted bridge rectifier240, which corresponds to a voltage of a first internal energy storagesystem 250 which is charged via the system transformer. In a number ofembodiments, first internal energy storage system 250 does not include abattery. Internal energy storage system 250 may, for example, include acapacitor system including one or more capacitors as, for example,illustrated in FIG. 1A. When discussing the embodiment of, for example,FIG. 1A, first internal energy storage system 250 may sometimes bereferenced as capacitor system 250 herein. In a number of embodiments,the capacitance of capacitor system 250 is insufficient to provideoperational power to implanted device 300 or is sufficient to holdenough energy to power the implanted device for a limited period of time(for example, in the range of approximately 10 milli-seconds to 1 secondor any range therebetween). The stored energy may, for example, besufficient to power implanted device 300 between bursts of energy fromexternal/primary coil 130 but not sufficient to normally operate device300 without the presence of external coil 130 supplying frequent burstsof energy In a number of representative embodiments for an implantedleft ventricle or heart assist pump system as device 300, operationalpower or normal operation includes powering the pump motor for onecomplete functioning period, e.g. one stroke, one cycle, one rotation,etc. In a number of embodiments, first internal energy storage system250 may, for example, store no more than approximately 260 Joule (J),130 J, 13 J, 6.5 J or even 1 J.

As described above, a normal heart provides 1.5 watts of useful power tosatisfy the body's metabolic needs. A severely impaired heart mightprovide half this power and a heart assist device may make up thedifference by providing, for example 0.75 watts of useful power. In anumber of embodiments, system 10 is adapted to provide at least 1 wattof power. In the case that implanted device 300 is a moving valve heartassist pump (sometimes referred to as a valve blood flow assist pump)as, for example, illustrated in FIG. 8 and discussed further below, pumpsystem 300 operates, for example, when the native heart is contracting,or about 40% of the time. Given limitations in efficiency, a movingvalve pump may require 5 to 35 (or even more) watts of power forassisting the failing heart.

Upon sensing that external coil 130 has been removed, implanted device300 may gracefully shutdown. Capacitor system 250 or other first energystorage system 250 may, for example, operate in a manner similar to afilter capacitor, (that is, filtering a rectified spread spectrum signal(discussed below) and/or filtering the frequent bursts of energy fromexternal coil 130 to provide a DC voltage to implanted device 300). In anumber of embodiments, capacitor system 250 may, for example, have acapacitance to store sufficient energy to power some portion of internalsystem 200 while external coil 130 is de-energized or powered off toenable, for example, swapping a discharged battery 120 for a chargedone. As an example, capacitor system 250 may hold enough energy to powerimplanted device 300 for several seconds while external battery 120 isreplaced with a charged battery. During this time, implanted device 300may switch to a low power mode to retain its memory and settings and maydisable higher power functions such as, but not limited to,communications and/or powering a motor or pump of implanted device 300.

Upon the return of external coil 130, implanted device 300 will start toreceive bursts of energy and may return to normal operation, includingenabling any high power functions that were disabled. If after apredetermined time period or if after the voltage on capacitor system250 reaches a minimum threshold voltage and implanted device 300 doesnot receive a burst of energy, internal system 200 or implanted device300 may store any necessary information such as, but not limited to,settings, current memory, device state, or any other necessaryinformation in nonvolatile memory for access and reconfiguration ofimplanted device 300 when power from external system 100 (via externalcoil 130) is restored.

When the measured voltage drops below a lower threshold (for example,nominally 12.5 VDC in a number of embodiments), first internalcontroller 210 causes a coded signal of that lower voltage state to betransmitted via an internal communication system including, for example,a first internal communication system or subsystem 270 to an externalcommunication system including, for example, a first externalcommunication system or subsystem 170. In a number of embodiments, thesignal is transmitted via radio frequency energy between internal coil230 and external coil 130. The signal may, for example, be transmittedat a different frequency from and independently of (for example, notoverlayed or superimposed upon) the energy transmission signal betweenexternal coil 130 and internal coil 230. First external communicationsystem 170 communicates with first external controller 110 which causesexternal coil 130 to be energized or powered on to transmit power fromexternal battery pack 120 to capacitor system 250. When the measuredvoltage on the output of implanted bridge rectifier 240 rises to anupper threshold (for example, 16.5 VDC in a number of embodiments) firstinternal controller 210 causes a coded signal of that higher-voltage orcharged state to be transmitted via first internal communication system270 to first external communication system 170. Once again, the signalmay be transmitted via radio frequency energy between internal coil 230and external coil 130. Like the lower voltage signal, such ahigher-voltage or “charged” signal may be transmitted by first internalcommunication system 270 at a different frequency from and independentlyof the energy transmission signal between external coil 130 and internalcoil 230. First external communication system 170 communicates receiptof the high-voltage signal to first external controller 110 which causesexternal coil 130 to be de-energized or powered off Under typicaloperating conditions, the measured internal voltage on the output ofbridge rectifier will be a sawtooth waveform that averages approximately14.5 VDC in the case that the lower threshold voltage is 12.5 VDC andthe upper or higher threshold voltage is 16.5 VDC.

In a number of embodiments, the power control system is also adapted toprovide a “watchdog”, “supervisory” or “status” function. It isimportant for the external control electronics (including, for example,first external controller) to be able to determine that the internalpower control system is functioning. For example, the absence of a lowervoltage signal or a higher-voltage (charged) signal from the powercontrol system to first external controller 110 during a period ofacceptable internal operating voltage could be erroneously interpretedas an indication that the internal or implanted circuitry is no longeroperational. To address such a failure risk, a coded “watchdog”,“supervisory” or “status” signal may be periodically transmitted fromthe implanted electronics to the external electronics. The supervisorysignal may, for example, be transmitted via radio frequency energybetween internal coil 230 and external coil 130. Like the lower voltagesignal and the higher-voltage signal, the supervisory signal may betransmitted by first internal communication system 270 at a differentfrequency from and independently of the energy transmission signalbetween external coil 130 and internal coil 230. First externalcommunication system 170 communicates receipt of the supervisory signalto first external controller 110. The supervisory signal may, forexample, be decoded by first external controller 110 and is used toreset a or supervisory timer. If the timer times out, first externalcontroller 110 may, for example, notify the patient via one or moreexternal indicators 160″ (see FIG. 2) adapted to provide information tothe patient of the supervisory time out in one or more manners adaptedto be sensed by the patient (for example, audibly, visually, and/ortactilely). Receipt of a lower voltage or a higher-voltage signal canalso reset the watchdog or supervisory timer. Therefore, in theabove-discussed embodiment, three different coded signals or messagesare communicated from the implanted power control system to the firstexternal controller 110: “lower voltage”, “higher voltage” or “charged”and “reset supervisory timer”. The absence of the supervisory signal canalso be used in conjunction with the current sensing capability of firstexternal controller 110 to further improve the reliability of misalignedcoil detection as described above.

In a number of embodiments, if the supervisory signal is not received ina predetermined period of time or timeframe (for example, 200milliseconds) or if the current sensing system 150 detects a highcurrent on the primary or external side, the power control system willturn off power transmission. The power control system will then attemptto recover control by periodically causing bursting of power viaexternal coil 130 for a defined length of time (for example, for 50milliseconds once every second). If the power burst is successful andsecondary or internal system 200 powers on, primary or external system100 will receive a communication signal (for example, either highvoltage, low voltage, or watchdog/supervisory as describe above). If thepower burst is unsuccessful, external system 100 may, for example, waitfor a period of time (for example, one second) and burst power again viaexternal coil 130.

In the case that external system 100/external coil 130 has beenpurposely removed, several mechanisms or methodologies may be used. Forexample, external battery pack 120 may be removed, which will removepower from external system 100. Removing power from external system 100means that it will no longer attempt the burst mode recovery of powercontrol for secondary system 200. Furthermore, external system 100 mayinclude an on/off switch or controller. If the user/wearer turnsexternal system 100 off or places it in an off state, external system100 will no longer attempt the burst mode recover of power control forsecondary system 200. External system 100 may even power itself offautomatically after a period of time (for example, 10-15 minutes) toconserve battery life. In such cases, external system 100 mayautomatically attempt to reestablish control of secondary system atpower-up. In another embodiment, external system 100 may include atimeout, such that if remote control via bursting cannot bereestablished after a period of time (for example, one minute) ofattempting to reestablish control, external system 100 may stopattempting and inform the user via some audible, visual, or tactilesignal (for example, an LED, a text display, spoken phrases, etc.).External system 100 would inform the user that control could not bereestablished and provide instructions to the user to re-enable theattempt when ready by, for example, pressing a button or taking someother action. Taking the action (for example, pressing the button) wouldre-enable the burst mode for another length of time (for example, 1minute) of periodic attempts (for example, every second). Thismethodology would, for example, cover the case wherein, for example, thewearer removes external system 100 for a five-minute shower withoutpowering external system 100 down or removing battery pack 120 and wouldprevent unnecessary transmission attempts and drain on battery pack 120while external system 100 was powered but control of internal system 200could not be reestablished.

In a number of embodiments of a sequence or methodology during initialpowering up of implanted system 200, first external controller 110 may,for example, provide a “burst” of power via external coil 130 andmonitor for a response/signal from implanted system 200 (for example, ahigher-voltage or charged signal or a “reset supervisory time” signal).If such a signal is received, first external controller can determinethat internal system 200 has properly powered on and initialized inresponse to the power burst from external system 100. If no signal isreceived, the first external controller may, for example, disable thepower (de-energize external coil 130) to avoid a high current situation,wait for a short period time, and then attempt the power burst again.Using this protocol or methodology, first external controller 110 canautomatically recover control of internal system 200 if, for example,external coil 130 and internal coil 230 become misaligned for a shortperiod of time and are then realigned. This methodology can assist inreducing the requirement of operator intervention and/or reduce theoccurrence of false misalignment signals for short, transientmisalignment events.

In a number of embodiments, data transmitted via the power control orfeedback system can be transmitted and/or received separately fromexternal coil 130 and/or internal coil 230, for example, using coilsseparate from external coil 130 and internal coil 230 or usingcommunication systems other than inductive coils. To conserve space,separate coils may, in a number of embodiments, be wound in the samevolume as external coil 130 and internal coil 230. FIG. 3B illustratesschematically an external data coil 130 a wound within the same volumeas external power coil 130 and an internal data coil 230 a would withinthe same volume as internal power coil 230 a. In certain embodiments, itmay be advantageous to have the internal coil used for both power andcommunications and have separate coils external for communications andpower. Having separate external coils may, for example, simplify theexternal circuitry or reduce noise caused by the power or communicationsignal to the other signal,

It is desirable for the size, power consumption and heat generation ofcomponents of implanted system 200 to be minimized. In a number ofembodiments, the frequency for transmission of the lower voltage signal,the higher-voltage signal and the reset-supervisory-timer or supervisorysignal was chosen to be approximately 13.56 MHz. Other frequencies canbe used, however. A frequency of 13.56 MHz is not often used in amedical or hospital settings, reducing the likelihood of interference.Further, a frequency of 13.56 MHz is significantly different from thefrequency range used for power transfer between external coil 130 andinternal coil 230, simplifying any required filtering or separation.Additionally, 13.56 MHz does not substantially radiate from the primarycoil 130 or the secondary coil 230 as a result of the small coil sizecompared to the wavelength, meaning that the primary coil 130 or thesecondary coil 230 do not create a source of interference. Therefore, byreciprocity, the 13.56 Mhz system is not significantly affected bysources of interference in the same frequency band. Although there arenumerous discrete and integrated circuit approaches for designing 13.56MHz generators and receivers, many such circuits are relatively large,consume significant power and/or generate significant heat.

In a number of embodiments, each of first external communication system170 and first internal communication system 270 of system 10 included aradio frequency receiver 172 including a commercially available radiofrequency identification or RFID reader chip and/or a radio frequencygenerator or transmitter 170 including a commercially available RFIDreader chip. RFID reader chips are designed to be small and consume lowpower. However, such RFID reader chips are not designed to be used aspairs in which the RFID reader chips communicate therebetween intransmit-receive communication applications. To the contrary, RFIDreaders are designed to communicate with RFID tags, which are designedor programmed to store data on thereon which can be read by the readerwhen the RIFD tag receives an electromagnetic energy signal from thereader. Using power from an internal battery (in the case of an activeor semi-active RFID tag) or power harvested from the reader'selectromagnetic field (in the case of a passive RFID tag), the RFID tagsends a radio frequency signal back to the reader. In a number ofembodiments hereof, commercially available RFID reader chips 172 and 272were programmed for a novel transmit-receive, chip-to-chip communicationconfiguration in which internal RFID reader chip 272 was caused by firstinternal controller 210 to transmit a radio frequency signal viainternal coil 230 and external coil 130 to external RFID reader chip172, which communicated the signal to first external controller 110. Ina number of embodiments, a high pass filter or a band-pass filter, a 50ohm impedance matching network, a 13.56 MHz L-C bypass and a DC blockwere used in each of first internal communication system 270 and firstexternal communication system 170 to couple the 13.56 MHz signalsthrough internal coil 230 and external coil 130. The 13.56 MHz L-Cbypass (not shown) was across the H-Bridge and bridge rectifier to shortthem at 13.56 MHz so they do not affect communications. In theembodiment described, the secondary or internal side is transmit onlyand the external or primary side is receive only, but both could beimplemented as transceivers for bi-directional communications.

An example of an RFID reader chip suitable to be adapted for use infirst internal communication system 270 and in first externalcommunication system 170 is the TRF7960 RFID reader, available fromTexas Instruments of Dallas, Tex. The TRF7960 RFID readers can be usedas general-purpose 13.56 MHz analog transceiver front ends by enabling adirect mode feature of the chip. The direct mode feature of the TRF7960bypasses the ISO RFID protocol encoders and decoders thereof so that aconnected microcontroller can transmit and receive data directly usingthe chip's on-board RF modulator. Transmitter chip or RF generator 272can, for example, be configured such that it generates the 13.56 MHz RFenvelope at full power by sending the appropriate configuration commandsto transmitting RFID reader chip 272 via its serial peripheral interface(SPI) bus. Transmitting RFID reader chip 272 is configured to use anon-off keying scheme when modulating the RF envelope, and it isconfigured into direct mode. Receiving RFID reader chip 172 isconfigured to expect an on-off keying scheme, and it is configured intodirect mode, but it is not configured to generate a 13.56 MHz RFenvelope, as this would conflict with the envelope generated bytransmitting RFID reader chip 272. Instead, receiving RFID reader chip172 is configured such that its receive circuitry is enabled. This modeis typically intended to allow a reader to measure an external RF fieldto determine if another reader is transmitting so that anticollisionmeasures may be taken. In the present case, however, the measurementmode allows receiving RFID reader chip 172 to sense the 13.56 MHzenvelope generated by transmitting RFID reader chip 272 and to receivedata as transmitting RFID reader chip 272 modulates that envelope. In anumber of embodiments, the signal from the transmitting and/or receivingRFID reader chip 272 is amplified.

First internal controller 210 (the transmitting microcontroller) can,for example, send data by toggling the MOD pin presented by transmittingRFID reader chip 272. When the MOD pin is toggled, the RF envelope ismodulated to produce bits (ones and zeroes) using the on-off keyingscheme. To simplify the transmission of data from first internalcontroller 210, the MOD pin can, for example, be wired to the transmitpin of a standard universal asynchronous receiver/transmitter (UART) offirst internal controller 210. This conformation allows the softwareexecuting on first external controller 210 to use the UART hardware tomanage the complex and critical timing required for binary datatransmission.

First external controller 110 (the receiving microcontroller) can, forexample, receive data via an input/output or IO pin presented byreceiving RFID reader chip 172 (for example, the IO_(—)6 pin of theTRF7960 chip). The IO pin represents the demodulated bit value describedby the RF envelope and is configured to expect an on-off keying scheme.To simplify the reception of data by first external controller 110, theIO pin can be wired to the receive pin of an UART of first externalcontroller 110. This conformation allows the software executing on thefirst external controller 110 to use the UART hardware to manage thecomplex and critical timing required for binary data reception. Use ofthe UART eliminates the need for software coding and transmissioncontrol.

Electromagnetic inductive power transmission of the type describedherein can generate significant electromagnetic interference, resulting,for example, in failure to meet regulatory requirements. In a number ofembodiments, system 10 and other systems hereof mitigate problemsassociated with electromagnetic interference by utilizing spreadspectrum frequency modulation for power transmission. The spreadspectrum modulation may be, but is not limited to, frequency hoppingspread spectrum (FHSS) or direct sequence spread spectrum (DSSS). Inthat regard, power is transmitted by external system 100 via external(primary) coil 130 at frequencies varying or spread within a range offrequencies under control of a spread spectrum algorithm. In a number ofembodiments, the frequency may, for example, be varied or spread betweenapproximately 120 kHz and approximately 130 kHz or between approximately120 kHz and approximately 126 kHz. In several such embodiments, thepower transmission is, for example, cycled from approximately 120 KHz toapproximately 126 KHz at 1 millisecond (or ms) intervals to achieve anominal 123 KHz transmission frequency. In a number of embodiments, thenominal power transmission frequency is between 50 and 500 kHz. Use offrequency spread spectrum hopping modulation “spreads” the fundamentaland harmonic energy across a number of frequency band channels on awider electromagnetic spectrum, resulting in, for example, decreasednarrowband interference and lower average power per channel. In a numberof embodiments, the average RF emissions generated are less than 25 μV/mat 300 m. The decreased narrowband interference enables system 10 totransmit relatively large amounts of power (for example, greater than 20watts, greater than 30 watts, or often between approximately 30 to 60watts) as required by implanted device 300 while meeting regulatoryrequirements for generated electromagnetic noise and interference.Although spread spectrum technology is known, the high Q or qualityfactor associated with transcutaneous energy transmission via primaryand secondary coils has previously prevented its use in transcutaneousenergy systems. In other words, it was previously believed thatbroadband power transmission was not feasible for transcutaneous energytransmission.

The system described herein was designed to have a low Q throughselection of the coil inductance to facilitate the use of spreadspectrum frequencies. A simple series RLC circuit has a Q of

$\begin{matrix}{Q = {{\begin{matrix}1 \\B\end{matrix}\sqrt{\begin{matrix}L \\C\end{matrix}}} \cong \begin{matrix}f_{0} \\{BW}_{3{dB}}\end{matrix}}} & (1)\end{matrix}$

and a resonant frequency of

$\begin{matrix}{f_{0} = \frac{1}{{SR}\sqrt{LV}}} & (2)\end{matrix}$

Combining (1) and (2) yields

$\begin{matrix}{{BW}_{3{dB}} = \frac{R}{QuL}} & (3)\end{matrix}$

In the above equations, Q is the quality factor, BW_(3 dB) is the halfpower bandwidth, f₀ is the resonant frequency, R is the circuitresistance, L is the circuit inductance and C is the circuitcapacitance.

As can be seen by these equations, maximizing the resistance andminimizing the inductance produces the greatest bandwidth. However, foran inductively coupled system transferring 10's of watts of power,maximizing the resistance produces unmanageable voltage levels andminimizing the inductance limits the effectiveness of the inductivecoupling. As an example, with 30 Watts delivered to the load at 15Vnominal, the equivalent resistance seen at the output of the secondarycoil is only 7.5 ohms.

For this reason, the inductive coupling system was not simply designedto resonate each side of the coupling transformer as done in previoussystems. Rather, the inductive coupling system was modeled and designedas a band-pass filter. An example of a typical band-pass filter isillustrated in FIG. 4A. Examining the equivalent circuit of atransformer (see FIG. 4B) shows that the transformer has the structureof a band-pass filter when capacitors or tuning capacitors are added inseries with the leakage inductances, X_(P) and X_(S). In general, thetuning capacitors and the leakage inductances form series elements ofthe band-pass filter and the magnetizing inductance forms a shuntelement. By selection of the inductance of the transformer, the leakageinductance and additional capacitors can be used to create a bandwidthwide enough to support a spread spectrum signal. Also, for an air coretransformer, which is used in several embodiments of the systems hereof,the core losses are zero, meaning R_(C) can be removed from the modelleaving only the magnetizing inductance X_(M). In a number ofembodiments, external or primary system 100 and internal or secondarysystem 200 are adapted such that a change of frequency of energy istransmitted from external coil 130 to internal coil 230 of +/−10%results in a change in transfer efficiency of no greater than or lessthan 10%.

Because the systems hereof include a primary and secondary designed tohave a low Q (defined in Equation 1 above as f₀/BW_(3 dB)), spreadspectrum signals can be used without the need to adjust the resonantfrequency or the center frequency of the system. In other words, thesystem does not require retuning to use frequency hopping signals. As aresult, in a number of embodiments, the system may include set or fixedtuning capacitors rather than a cumbersome and power-consumingreconfigurable tuning network. Moreover, because the system may have aset of fixed resonance, the primary driver can adjust the frequency(frequency hop) of the power transmission signal without informing thesecondary of the frequency change.

Additionally, because the system has a low Q (broad bandwidth),sophisticated spread spectrum signals can be used that have more thanone frequency component at a given time such as direct sequence spreadspectrum. In a number of embodiments hereof, the Q of the system is lessthan 100, less than 50, less than 10, or even less than 5. In a numberof such embodiments, the Q of the system is less than 10 or less than 5.

In a number of embodiments hereof, the resonant frequency of the primarycoil and/or the secondary coil (and, thus, the center frequency of thespread spectrum power transmission signal) may be adjusted in responseto, for example, misalignment of the primary coil and the secondarycoil, in response to changes in component values which may drift withtime, or in response to the temperature of the external system. Tunedcapacitors may, for example, drift in value over their lifetime as aresult of factors such as moisture absorption. The tuning of the primarycoil and/or the secondary coil may be adjusted in response to, forexample, misalignment of primary coil and secondary coil, in response tochanges in component values which may drift with time, or in response tothe temperature of the external system. In such embodiments, areconfigurable tuning network may, for example, be used. After any suchadjustment in resonant or center frequency, the spread spectrumalgorithm may be centered around the new resonant frequency. Asfrequency changes during spread spectrum algorithms hereof, however,there is no need to tune either the primary coil or the secondary coilto the various frequencies used in the spread spectrum algorithm.

A simulation schematic for the inductive coupling system designed isshown in FIG. 4C. For simulation purposes, the coupling coefficient wasassumed to be 0.8 to model the leakage inductances, and the load was 7.5ohms (30 Watts at 15V). The equivalent series resistance (ESR) of eachcoil was included in the transformer model. The results can be seen inFIG. 4D, which shows that the transfer efficiency from Vin to Vout isvery good from 100 kHz to almost 300 kHz. A simulated band-pass model ofthe inductive coupling system can be seen in FIG. 4E, where the leakageinductances have been assumed to be 20% of the coil inductances and themagnetizing inductance as 10 uH. As can be seen in FIG. 4F, theband-pass model results show very good agreement with the transformersimulation.

To demonstrate the importance of designing the inductive system using aband-pass filter model, the system in FIG. 4C was modified by scalingthe transformer inductances down by a factor of four. Equation 3 wouldsuggest, although the system is not a simple RLC, that reducing theinductance should increase the bandwidth. To ensure resonance at 125kHz, the capacitors were increased by a factor of four to keep the sameresonant frequency as FIG. 4C as calculated using Equation 2. Theschematic can be seen in FIG. 4G. The results shown in FIG. 4H show aresonance at 125 kHz as predicted by Equation 2 but the bandwidth iscomparatively very narrow. This analysis demonstrates that the inductivecoupling system is beneficially designed to resonate and be constructedas a band-pass filter to have sufficient bandwidth to support a spreadspectrum signal.

FIG. 5A shows that the maximum conversion efficiency is achieved bymaintaining the output power at 30+ Watts (maximum load). However, whenlower power is required at the load, reducing the output power bychanging the primary drive voltage reduces the conversion efficiency.Therefore, it is more efficient to enable the power transfer at a powerlevel of 30+ Watts and then disable the transmission for a given periodof time. In a number of embodiments, the transfer efficiency of thesystem (where transfer efficiency is defined asP_(OUT-DC)/P_(IN-DC)*100) is greater than 75%, greater than 80% orgreater than 85%. During the disabled time, a capacitance on thesecondary (internal) side of the inductive transfer can provide power tothe load (implanted device). When additional power is required, theprimary (external) side can be enabled to recharge capacitor system 250.In general for power levels around 30 Watts, any capacitance designedinto the secondary or internal system with reasonable physical size forthe load (implanted device 300) will be insufficient to operate the loadfor any appreciable time period. Therefore, the primary will frequentlybe enabled or energized and disabled to provide power to the secondary.For example, in a number of embodiments the internal secondary systemmay function for only less than one second before requiring capacitorsystem 250 to be recharged by the primary. As described above, system 10is designed to hold the voltage on capacitor system 250 within a voltagewindow having a lower and upper threshold. The system efficiency isdesigned so the transfer efficiency is not affected by the exact voltagelevel seen on capacitor system 250. This can be seen on the graph ofFIG. 5A by examining the conversion efficiency at 30+ Watts for 14, 15,and 16 volts.

FIG. 5B illustrates changes in the power requirements of the load(implanted device 300), the external/primary output voltage and thevoltage of the internal/secondary capacitor system 250 over a period oftime for several embodiments hereof. As illustrated, the powerrequirement of the implanted device 300 is initially approximately 100%.Power is transferred via primary or external coil 130 via bursting oron/off cycling of external coil 130 (done, for example, by On-Off keyingor On-Off modulating the power transmission frequency, orenabling-disabling the primary driver or H-bridge driver) at apredetermined power or voltage amplitude (or amplitude range)sufficiently high to provide a predetermined efficiency (for example, atleast 75% or at least 80%). In general, it is desirable to maximizeefficiency. After a period of time, the power requirement of implanteddevice 300 decreases to 50% in FIG. 5B. As illustrated in FIG. 5B, theamplitude and frequency of the voltage output of external coil 130 ismaintained at the predetermined amplitude (or amplitude range), but theduration of the power bursts decreases as compared to the case of a 100%power requirement. After a period of time, the power requirement ofimplanted device 300 further decreases to 10% in FIG. 5B. Once again,the amplitude and frequency of the voltage output of external coil 130is maintained at the predetermined amplitude (or amplitude range), butthe duration of the power bursts decreases as compared to the case of a50% power requirement. Upon the power requirement of implanted device300 increasing from 10% to 100% in FIG. 5B, the amplitude and frequencyof the voltage output of external coil 130 is maintained at thepredetermined amplitude (or amplitude range), but the duration of thepower bursts increases. Preferably, the duration of the power bursts isat least several cycles at the center frequency of the spread spectrumsignal. As described above, capacitor system 250 operates in a mannersimilar to a filter capacitor to filter the rectified spread spectrumsignal and to filtering the frequent bursts of energy to provide a DCvoltage in a predetermined range of voltages to implanted device 300.The amplitude of the power or voltage output of the external system100/external coil 130 can, for example, be maintained within 20% of fullpower, within 10% of full power or at full power when external coil 130is energized.

As described above, system 10 is designed to transfer power using spreadspectrum signals. FIG. 5C shows that the bandwidth of system 10 has beendesigned to have a low enough Q to enable spread spectrum transfer. Ascan be seen, a ±10% change in the frequency compared to the centerfrequency reduces the transfer efficiency by only approximately three tofive percentage points which is less than 10%.

Previous solutions have varied the duty cycle of the H-bridgefundamental drive frequency to adjust the output power. As can be seenfrom FIG. 5D, reducing the duty cycle reduces the amount of powerdelivered to the load, but it also reduces the transfer efficiency ofthe system which is undesirable because it generates unwanted heat(loss) and reduces the run-time of the primary side battery pack.

As described above, the internal control system of internal system 200can, for example, include second internal controller 220 (including, forexample, a microcontroller or microprocessor) to monitor and controlimplanted device 300. Either first internal controller 210 or secondinternal controller 220 can also, for example, monitor one or moresensors, sensor systems or sensor arrays 280 and/or 280′ that caninclude one or more sensor (for example, pressure sensors, flow sensors,force sensors, temperature sensors, pH sensors etc.). To enable externalmonitoring and/or control of implanted device 300, sensor system 280and/or other internal or implanted components, internal system 200 can,for example, include a second internal communication system 290.External monitoring and/or control of various internal system componentscan, for example, be accomplished using wireless (for, example, radiofrequency) communication between second internal communication system290 of internal system 200 and one or more external communicationsystems/external controllers, including, for example, second externalcommunication system 190 and first external controller 110 of externalsystem 100. The frequency used for communication between second internalcommunication system 290 of internal system 200 and one or more externalcommunication systems/external controllers can be different from thefrequency range of power transmission and different from the frequencyrange of communication between first internal communication system 270and first external communication system 170. A frequency range of 402MHz-405 MHz has, for example, been recommended for medical implantcommunication systems (MICS) and has been implemented in the UnitedStates under the Federal Communications Commission (FCC) rules 47 CFR95.601-673, and in Europe under the European TelecommunicationsStandards Institute (ETSI) Standard EN 301 839-1. Remote communicationswith second internal communication system 290 can, for example, followthe MICS guidelines to transfer digital data bi-directionally betweeninternal system 20, including the internal controller(s) thereof andimplanted device 300, and one or more external communicationsystems/external controllers. Such external communication systems and/orexternal controllers can, for example, be components of external controlsystem 100, a patient station 500 (which can, for example, include acharger 510 for rechargeable battery 120), a caregiver station 600 (foruse, for example, by a physician and/or other caregiver) and amanufacturer station 700 (see FIG. 6). To minimize power consumption,the digital transmission link can be turned off when not in use. A lowpower wake-up signal (for example, a 2.4 GHz wake-up signal) can, forexample, be used to turn on the transmission link. MICS-based internalor implantable communication units and external communication units orbase stations suitable for use herein are for example, available fromZarlink Semiconductor Inc. of Ottawa, Canada.

Using, for example, MICS, second internal communication system 290and/or second external communication system 190 can establish arelatively high-speed, longer-range (up to, for example, approximately 2meters) wireless link between internal system 200 and patient station500, caregiver station 600 or manufacturer station 700. The wirelesscommunication link can, for example, be used to send patient health anddevice operating data to bedside patient station 500 via a radiofrequency, wireless communication system 520 of patient station 500.Data can, for example, be transmitted or forwarded from patient station500 via a network communication system 530 (using, for example, landlinetelephone service, wireless telephone service, the Internet etc.) to,for example, caregiver station 600 via a network communication system620 of caregiver station 600. When the patient is in the caregiver'soffice or otherwise in the vicinity of caregiver station 600 (which, canfor example, include a specific or general purpose computer), thewireless, digital communication protocol (via communication between awireless communication system 610 of caregiver station 600 and secondinternal communication system 290 or second external communicationsystem 190) can be used by the caregiver to, for example, downloadoperating parameters to second internal controller 220 for implanteddevice 300, to, for example, configure operation of implanted device 300for patient-specific operation. Alternatively, a wired connection(using, for example, a universal serial bus (USB) connection) can beformed between a port 632 of a wired communication system of caregiverstation 600 and a port 194 of a wired communication system 192 ofexternal system 100.

Using manufacturer station 700 (which, can for example, include aspecific or general purpose computer), a manufacturer can, for example,use a communication link (via a wireless communication system 710 or avia a communication port of a wired communication system 630) todownload operating firmware to second internal controller 220 forimplanted device 300 from manufacturer station 700. Manufacturer station700 can serve as a service and diagnostic station. Manufacturer station700 can be used to monitor device operational information and to uploaddevice operational “configuration” parameters. Manufacturer station 700can also include a network communication link 720 to, for example,communicate with external system 100, patient station 500 or caregiverstation 600. Manufacturer station 700 can also include a wiredconnection system 730 (for example, a USB connection) including acommunication port 732 to form a wired communicative connection withport 194 of wired communication system 192.

Second internal controller 220 can, for example, monitor and recordvarious parameters of the operation of implanted device 300 over time(similar to a “flight controller”) to provide such information to acaregiver and/or a manufacturer (for example, operating voltages,currents etc.). Caregiver station 600 can, for example, be used toprogram operation of implanted device 300 on a per patient basis. In anumber of embodiments, caregiver station 600 can periodicallycommunicate with patient station 500 (for example, nightly) via, forexample, the internet to enable a physician or other caregiver tomonitor patient and device status over extended periods of time.

As discussed above, in a number of embodiments, implanted device 300 isa blood flow assist device as, for example, described in U.S. patentapplication Ser. Nos. 3/370,113, 13/370,137 and 13/370,155 and PCTInternational Patent Application No. PCT/US2012/024572. Such assistdevices are moving valve heart assist pumping systems 300 which may, forexample, be placed in line with a blood vessel such as the ascendingaorta as illustrated in FIG. 7. In pump system 300, motor 320 impartsreciprocal motion to a valve assembly 330 including closure members 332which close upon forward motion of valve assembly 300 (relative to bloodflow from the heart through pump system 300) and open upon rearwardmovement of valve assembly 330 (see FIG. 8). Valve assembly 300 can, forexample, be connected in the vicinity of the perimeter thereof to aflexible conduit 304 through which blood flows.

Control parameters of pump system 300 that can, for example, be adjustedby a caregiver via caregiver station 500 include, but are not limitedto, timing and/or frequency of the movement of valve assembly 330. Inthe case that a pacemaker functionality is included (for example, as acomponents of second internal controller 220), pacing of the heart canalso be adjusted by a caregiver. Various sensors can be used inconnection with pump system 300 such as a flow sensor 282 (for example,a thermistor) and a pressure sensor 284, each of which can be placed influid connection with the flow path of blood through pump system 300(see FIGS. 8 and 9). Various other sensors 286 can, for example, beplaced in operative connection with pump system 300 (for example, acurrent sensor in operative connection with motor 320, a force sensor inoperative connection with valve assembly 300, etc.) to measure variousoperational parameters of pump system 300. Leads 288′ can be placed inoperative connection with the heart of the patient can be used to sensethe electrical activity and rate of the heart for use in timing of themovement of valve assembly 330. For example, the P wave of the heartelectrocardiogram or a portion of the QRS complex can be used to timevalve movement. Leads 288′ can also be used in pacing the heart. Othersensors 280′ can, for example, measure various patient physiologicalsensor (for example, atrial pressure, left ventricle pressure,temperature, respiration variables etc.). As illustrated in FIG. 9,sensors as described above can be placed in communicative connectionwith first internal controller 210.

In a number of embodiments as described above, various sensor leads wereconnected to first internal controller 210 and not to second internalcontroller 220, which controls pump system 300. This division can, forexample, be effected to allow second internal controller 220 to focusits activity upon implanted device/pump system control. As describedabove, pump system (and/or other implanted device) control, sensormonitoring, communication control etc., can be accomplished via a singlecontroller or such tasks can be distributed over two or morecontrollers. Moreover, various signals can be redundantly routed orsplit between two or more microcontrollers.

A caregiver can, for example, observe measures of flow and pressure(and/or other measured properties of blood or parameters of pump system300), either during blood flow assist or absent blood flow assist. Withthe valve assembly 330 of pump system 300 set in the “off” mode, thevalve assembly is stationary and in an open state, the caregiver canobserve the patient's unassisted blood flow profile and caregiverstation 500 can, for example, integrate the flow signal to calculateheart stroke volumes as well as cardiac output expressed in liters perminute or LPM terms. The caregiver can then add moving valve assist byactivating valve assembly 330 using, for example, test modes and timingadjustments to determine which moving valve operating mode is best forthe patient (for example, to provide a determined or desired assistedcardiac output). Either or both of first external controller110 orsecond internal controller 220 can then be programmed for automaticmoving valve operation as the patient leaves the caregiver's/physician'senvironment.

Output from sensors which provide a measurement of one or moreparameters of the blood (including, for example, parameters of bloodflow) such as sensors 282 and 284 and/or other sensors can be used insetting parameters for pump system 300 as well as for providingclosed-loop control of pump system 300. As known in the computer arts,control algorithms, which can include artificial intelligence routines,can be programmed into the processors (for example, microprocessors) ofsystem controllers, including, for example, if-then statements, as wellas other types of automatic logical control.

In addition to physiologic output signals such as flow and pressure,motor performance parameters or signals can also be sensed andperiodically recorded. These signals can, for example, include or berelated to motor current, motor commutation, timing events, as well asmotor speed and its derivatives of valve speed, valve position and valveacceleration. These signals can, for example, be transmitted to secondinternal controller 220 via implanted leads connecting second internalcontroller 220 to pump system 300 and to the patient's heart. Using theknown relationship of motor current to motor torque, the system will becapable of determining the force being supplied to the moving valve. Byadditionally determining/measuring the pressure behind the valve, thesystem will be capable of, for example, calculating the pressuredifference across valve assembly 330. The pressure difference acrossvalve assembly 330 can also be measured more directly using anappropriate sensor or sensors. This pressure difference when multipliedby valve assembly velocity and integrated during the forward stroke ofvalve assembly 330 provides valve assembly work and power information.With pump system 300 off, flow and pressure sensing similarly provideunassisted heart work and power performance information. With pumpsystem 300 on, the relative energy contributions of the heart and pumpsystem 300 can be calculated and the operating parameters of pump system300 can be adjusted to provide the best possible outcomes for thepatient as judged by the caregiver.

Referring to, for example, FIGS. 1B, 5E, 11, and 12, in a number ofrepresentative embodiments, systems hereof were constructed as shown inFIG. 1B and operated as shown in FIGS. 5E, 11, and 12. In the embodimentof system 10 a of FIG. 1B, external system 100 a was designed to bepowered by, for example, a single battery pack including four seriesconnected rechargeable battery cells, collectively referred to herein asthe battery 120, having a fully charged maximum voltage of 16.8V and afully discharged minimum voltage of 12V. Battery 120 a supplied power tothree DC/DC converters. More or less than four external battery cellsmay be arranged in an appropriate series/parallel configuration as knownto those skilled in the electrical arts to increase the battery packoperating time between charges and/or operating life without changingthe designed operating voltages of the systems hereof. A plurality ofredundant external battery packs is not required.

In system 10 a, a first DC/DC converter provided 12V to an H-Bridgedriver (for example, a model HIP4081A high frequency H-Bridge driveravailable from Intersil Corporation of Milpitas, Calif. USA). TheH-Bridge driver drove NFETS 140 a to produce the drive frequency andpower supplied to tuned primary coil 130 a, which included eight turnsof 12 AWG litz wire. Primary coil 130 a was designed to resonate with acenter frequency of approximately 122.5 kHz with a bandwidth wide enoughto cover 120-130 kHz. The resonance was achieved with a single tuningcapacitor in series with primary coil 130 a. Two tuning capacitors, oneon each side of primary coil 130 a, may optionally be used to balancethe system and to reduce switching noise on primary coil 130 a to ensureEMI compliance as, for example, required by the FCC.

A second DC/DC converter provided the power to the H-bridge NFETs 140 athat effectively drove primary coil 130 a. The 10V output of the secondDC/DC passed through a current sensor circuit 150 a including, forexample, a sense resistor and a current sense amplifier. In a number ofembodiments, the current sensor circuit 150 a would disable the H-bridgedriver if the current exceeded ten amps.

A third DC/DC converter provided the power to an external controlsystem/controller 110 a (for example, a microcontroller) and an externalcommunication system 190 a (for example, including radio frequencytransceiver circuitry) at 3.3V. External controller 110 a was used tocontrol the operation of the H-bridge and radio 190 a. Externalcontroller 110 a enabled or disabled the H-bridge driver and suppliedthe drive frequency to the H-bridge driver. Additionally, the externalcontroller 110 a was programmed to frequency hop the drive frequency tothe H-bridge driver to, for example, help reduce EMI from primary coil130 a. In a number of embodiments, the frequency hopped from 120 kHz to126 kHz in 1 kHz steps. The dwell time on each channel was, for example,1 ms with each channel getting equal active time. At 1 ms, the number ofcycles on a channel was equal to 1 ms times the channel frequency. As anexample, a 120 kHz drive frequency corresponds to 120 cycles at 120 kHzin 1 ms. Therefore, the output sequence from external controller 110 awould be as follows: 120 cycles at 120 kHz, followed by 121 cycles at121 kHz, followed by 122 cycles at 122 kHz, followed by 123 cycles at123 kHz, followed by 124 cycles at 124 kHz, followed by 125 cycles at125 kHz, followed by 126 cycles at 126 kHz, then the sequence isrepeated continuously. The resulting average EMI from primary coil 130 awas reduced to one seventh of that of a comparable system in which aspread spectrum control algorithm was not used. Additional channels canbe added and the bandwidth may be increased. The system may, forexample, cover a 10 kHz bandwidth with eleven channels having 1 kHzchannel spacing. External controller 110 a was also designed to receivecommands from external communication system 190 a. Externalcommunication system 190 a was adapted, for example, to receiveinformation/commands from internal system 200 a via an internalcommunication system 290 a (for example, including radio frequencytransceiver circuitry). In a number of embodiments, the radio frequencycommunication was in the 915 MHz band and used a robust modulationprotocol of direct sequence spread spectrum (DSSS) to help eliminatepotential interference from other electronic and wireless devices.Additionally, the DSSS can be frequency hopped to create an extremelyrobust signal. The 915 MHz DSSS smears the energy in the RFcommunication signal across a bandwidth greater than 500 kHz. Frequencyhopping the DSSS signal moves the center frequency of the smeared signalaround in the band. The resulting frequency hopping direct sequencespread spectrum signal becomes very immune to interference. In a numberof embodiments of system 10 a, communication signals were nottransmitted via external coil 130 a and internal coil 230 a.

Internal system 200 a included secondary coil 230 a and a series tuningcapacitor. The capacitor was used to set the resonant frequency toapproximately 122.5 kHz. Two tuning capacitors, one on each side of thesecondary coil, may optionally be used to balance the system and toreduce switching noise on the secondary coil to ensure EMI complianceas, for example, required by the FCC. A safety shunt 232 a was placedacross tuned secondary coil 230 a. In a number of embodiments, shunt 232a would activate only in the event of a system failure or error. Shunt232 a, shorts the output of secondary coil 230 a to ensure no moreenergy is provided to internal system 200 a which could cause excessheat and potential excess heating of body tissue. Shunt 232 a wasdesigned to automatically activate if a 21V over voltage protectioncircuit 262 a was activated for longer than a predetermined period oftime. Shunt 232 a could also be activated by an on-board temperaturesensor.

The output of secondary tuned coil 230 a was provided to a full-waverectifier constructed with low-loss schottky diodes. The output of therectifier was filtered by a first energy storage system such as acapacitor system 250 a including, for example, five 1000 uF 25Velectrolytic capacitors. Capacitor system 250 a also held a small amountof energy to allow response time for the communication of commands frominternal system 200 a to external system 100 a. The commands weredependent on the voltage on capacitor system 250 a. In a number ofembodiments, internal system 200 a would inform external system 100 awhen the voltage was above 17V, was below 15V, or when it was between15V and 17V. The voltage monitoring was done periodically but at afrequency essentially making it continuous monitoring. In severalembodiments, the voltage on capacitor system 250 was monitored by twocomparators that sent digital signals to internal controlsystem/controller 210 a (for example, a microprocessor). Internalcontroller 210 a determined the status and used internal communicationsystem 290 a (for example, a 915 MHz DSSS system) to send wirelessinformation/commands to external system 100 a (via externalcommunication system 190 a). Internal system 200 a included a DC/DCconverter to transform the 17V signal to 3.3V to run internal controller210 a and radio 290 a.

In a number of studies, the efficiency of the power transfer from the10V DC/DC converter to the output of the rectifier (DC in to DC out) wasapproximately 90% with 35 W of output power.

The systems hereof are well suited for use in connection with, forexample, implantable systems wherein a failsafe mode of operation isprovided should an external/primary source of power beremoved/deactivated. As described above, in a number of embodiments,internal system 200 a includes or is in operative connection with animplanted device such as, for example, moving valve pump system 300. Ina number of embodiments, pump system 300 was connected in series withthe heart to assist the heart in pumping blood and is designed such thatvalve assembly(ies) 330 thereof are in a normally open state asdescribed above. In that regard, closure members 332 (which may bebiased toward an open state—for example, via springs or other biasingmembers) close upon forward motion of valve assembly 300 (relative toblood flow from the heart through pump system 300) and open uponrearward movement of valve assembly 330 (see FIG. 8). Valve assembly 300will open (as a result of biasing and/or the momentum of natural bloodflow) if the secondary voltage is lost as a result of, for example,absence or deactivation of the external system 100 a. Valve assembly 330of pump system 300 will open in response to the heart pumping and willnot substantially impede blood flow. FIG. 8 illustrates closure members332 of valve assembly 330 in an open state during, for example, abackstroke of valve assembly 330 or when, for any reason, pump system300 is not active (for example, because of power loss or failure of oneor more components of pump system 300).

The normally open state of valve assembly 330 of pump system 300 reducesor eliminates the need for an internal energy storage unit that couldoperate pump system 300 without the operating presence of externalsystem 100 a. Internal energy storage (via, for example, ininternal/implanted rechargeable battery) reduces the lifetime of aninternal/implanted device. In that regard, internal energy storagesystems require periodic service by surgery. The systems hereof do notsuffer from that limitation. The operational power for internal system200 a is continuously supplied in real-time by external system 100 a forextended periods of time (for example, for the charge life of battery120 a); and pump system 300, as described above, is designed to notsubstantially impede the flow of blood therethrough when external system300 is removed.

In a number of embodiments, closure members of valve assemblies of pumpsystems hereof are opened and/or closed in an active manner as describedin U.S. patent application Ser. No. 13/370,155 and PCT InternationalPatent Application No. PCT/US2012/024572. In that regard, testingdemonstrated that actively moving the closure members of a valveassembly toward a closed position to close the valve opening at thebeginning of the forward stroke can increase pumping efficiency byapproximately 50 percent. Actively moving closure members of a movingvalve pump system toward a closed state is thus desirable for thepurpose of increasing pump efficiency. As used herein, the terms such as“active” or “actively” refer to control using one or more devices,mechanisms, systems and/or methods for moving closure members toward anopen or closed position or state independent of the force asserted uponthe closure members by blood flow. Actively moving the closure membersof a valve assembly in a moving valve pump system may, for example, beeffected using a mechanism or system that activates closure membermovement based on the position of the valve assembly.

In a number of embodiments, closure members similar to closure members332 are used in pump systems hereof wherein the axles, shafts or rodsfixed to the closure members are extended to pass through at least aportion of the valve support structure of the valve assembly and toextend outside of the flow conduit of the pump system. FIGS. 10A through10D illustrate an embodiment of a valve assembly 1300 a including avalve support structure 1310 a (see FIG. 8A), closure members 1332 a andshafts 1332 a. Shafts 1332 a extend through at least a portion ofsupport structure 1310 a so that a portion of shaft 1332 a is outside ofand/or sealed from the blood flow path through flow conduit 304 of pumpsystem 300 (or another moving valve pump system hereof). A flexible seal1340 a, which can be positioned within a seating formed in supportstructure 1310 a, is fixed to shaft 1332 a, which passes through anopening or passage 1342 a of seal 1340 a.

To assist in providing proper alignment and relatively free movementthereof, each shaft 332 a can cooperate with (for example, pass through)one or more bearings. In the embodiment of FIGS. 10A through 10D, eachshaft 1332 a is mounted within, for example, two rolling elementbearings 1350 a to properly align each shaft 1332 a and minimize torquerequired to rotate closure members. Because bearings 1350 a may beexposed to a corrosive environment, they can, for example, be formedfrom a corrosion resistant material such as nitrided martensiticstainless steel or a ceramic material. Each shaft 1332 a of a closuremember 1330 a (two in the embodiment illustrated in FIGS. 10A through10D) may, for example, include two bearings 1350 a positioned on shafts1332 a at opposite ends of closure members 1330 a. In the illustratedembodiment, each bearing 1350 a is sealed from the blood flow path byseals 1340 a.

External to (or radially outward from, with reference to axis A₁—seeFIG. 10A) bearings 1350 a, at least one end of shafts 1332 a includes anextending section 1332 a′ (which can be a part of shaft 1332 a orconnected thereto). Rotational activation of extending sections 1332 a′results in rotation of closure members 1330 a operatively connectedthereto in an opening or closing direction via an activating system suchas activating system 1500 illustrated, for example, in FIGS. 10A through10D.

In the illustrated embodiment, valve support structure 1310 a is formedin two sections 1312 a and 1314 a which are separable from each otheralong a plane generally perpendicular to axis A₁ of pump system 1300.Such a construction may facilitate assembly valve assembly 1300 a,including the mounting of closure member shafts 1332 a while, forexample, in operative connection with associated seals 1340 a andassociated roller element bearings 1350 a in valve support structure1310 a. FIG. 10B illustrates mounting of those components in section1312 a of valve support structure 1310 a. In FIG. 10C, section 1312 a isillustrated without seals 1340 a in operative connection with shafts1332 a to illustrate the seatings therefor formed in section 1314 a.Similar seatings (not shown) are formed in section 1314 a.

In the embodiments illustrated in FIGS. 10A through 10D, closure memberactivating system 1500 is formed at least partially integrally withvalve support structure 1310 a of valve assembly 1300. However, theactivating system can be formed separately from and in operativeconnection with valve assembly 1300. For example, activating system 1500may be operatively connected to an annular connector 410 (driven bymotor 320) within pump system housing 302. Activating system 1500includes a positioning mechanism such as a positioning gear 1510 inoperative connection with (for example, keyed thereto) extendingsections 1332 a′ of shafts 1332 a. A rack 1520 including teeth on twosides thereof, which are adapted to mesh with positioning gears 1520, isoperatively connected between positioning gears 1510 a. A change in theposition of rack 1520 along a line generally parallel to axis A₁ drivespositioning gears 1510 and, thereby, shafts 1332 a and closure members1330 a. In that regard, rotational motion of positioning gears 1510imparts rotational motion to extending sections 1332 a′.

An abutment member (not shown in FIGS. 10A through 10D, but, forexample, positioned at a fixed position relative to (and within) housing302 (with reference to pump system 300) can, for example, contact rack1520 as valve assembly 1300 a moves rearward (represented by arrow R inFIG. 10A) in the vicinity of the rearwardmost position of valve assembly1300 a to drive rack 1520 in a forward direction. Forward motion of rack1510 rotates positioning gear 1510 on the right side (from theperspective of the viewer of FIGS. 10A through 10D) of rack 1520 in acounterclockwise direction and rotates positioning gear 1510 on the leftside of rack 1520 in a clockwise direction to move closure members 330 atoward a closed position as illustrated in FIGS. 10A through 10C. As,for example, illustrated in FIG. 10D, rack 1510 can be movable through alinear bearing 1530 which limits movement of rack 1520 to movement in asingle linear direction. Each side of linear bearing 1530 may, forexample, operate in the manner of a linear rolling element bearing. Eachside of linear rolling element bearing 1530 may, for example, includetwo geared roller elements 1532. In the illustrated embodiment, linearrolling element bearing 1530 is positioned within a seating 360 a whichis attached to or formed integrally or monolithically with section 312a.

Rack 1520 need, for example, travel only a short distance between thepositioning gears 1510 to activate closing or opening of both closuremembers 1330 a. In one embodiment, positioning gears 1510 rotate closuremembers approximately 90 degrees from a fully open position illustratedin FIG. 10D, wherein closure members 1330 a are oriented generallyparallel to the direction of bulk flow of blood through valve opening1320 a to a fully closed position as illustrated in FIGS. 10A through10C, wherein closure members 1330 a are oriented generally perpendicularto the direction of bulk flow of blood through opening 1320 a.

As described above in connection with valve assembly 1300, pressure fromthe flow of blood through valve opening 1320 a (particularly duringrearward movement of or the backstroke of valve assembly 1300 a) tendsto force closure members 1330 a to an open position. However, amechanism or system can be provided to, for example, cooperate withactivating system 1500 to bias closure members 1330 a to an openposition or state (that is, to actively cause movement of closuremembers 1330 a toward an open position or state, which is a default ornormal state). Activating system 1500 may, for example, include or havein operative connection therewith a biasing mechanism or system 1540 athat applies force to rack 1510 to cause rack 1510 to move (in thedirection of arrow R in FIG. 10A) to open closure members 1330 a.Biasing mechanism 1540 a may, for example, bias rack 1510 to movesufficiently to rotate closure members 1330 a (via positioning gears510) to the fully open state illustrated in FIG. 10D when valve assembly1330 a is in its backstroke or when, for any reason, pump system 1300 oranother moving valve pump system incorporating valve assembly 1300 a isnot active (for example, because of power loss or failure of one or morecomponents of the pump system). In the embodiment illustrated in FIGS.10A through 10D, biasing mechanism 1540 includes a spring positionedwithin a seating 1370 a attached to or formed integrally ormonolithically with section 1314 a. Biasing mechanism or system 540assists in preventing extended blockage of the blood flow path in anycircumstance.

FIG. 11 illustrates a flow chart of an embodiment of a method ofoperation of the external system of FIG. 1B. Referring to FIG. 11, in anumber of embodiments, external system 100 a starts by powering upsystem 10 a by starting the frequency hopping clock (represented by CLKin FIG. 1B). Power is transferred by turning on primary coil 130 a byenabling the H-Bridge driver. External system 100 a then waits for amessage from the internal system 200 a or an over-current condition. Anover-current condition may, for example, occur when the internal system200 a is not present. In a number of embodiments, external system 100 awaits approximately 200 ms. If no message from the internal system 200 ais received, system 10 a is disabled by disabling the H-bridge driverand stopping the frequency hopping clock. External system 100 a thenwaits a period of time (for example, 1 s) and tries again. If externalsystem 100 a receives a message from internal system 200 a, it isanalyzed and primary coil 130 a of system 10 a is, for example,enabled/energized if the secondary/internal voltage is too low ordisabled/de-energized if the secondary/internal voltage is too high asdescribed above. Additionally, in a number of embodiments, system 10 aautomatically activates the power transfer if primary coil 130 a hasbeen off for more than a determined time T_(MAX), for example 5 ms, asshown in FIG. 5E. This automatic activation avoids unnecessary dischargeof secondary capacitors 250 a during low load conditions. Additionally,this automatic activation helps to reduce the ripple voltage oncapacitor system 250 a. The sequence described above and in FIG. 11continues as long as the external system 100 a is powered up by itsbattery pack.

Referring to FIG. 12, internal system 200 a starts when capacitor system250 a reaches a voltage level sufficient to power up internal controller210 a. Internal system 200 a sends messages to external system 100 ausing internal communication system 290 a and the operatively connectedantenna. As described above, if the voltage on capacitor system 250 a isabove a predetermined maximum threshold or below a predetermined minimumthreshold, a command to alter the system status is sent by internalsystem 200 a. Internal system 200 a also automatically sends a statuscommand every 5 ms to ensure external system 100 a has the latestinformation and can confirm that internal system 200 a is still present.This methodology is, for example, illustrated in FIG. 5E, whereinT_(MAX) is the maximum time external/primary coil 130 a will bedeactivated before internal system 200 a automatically sends a commandto activate external coil 130 a even though V_(MIN) has not yet beenreached. Also, in anticipation of heavy loads, internal system 200 maypre-charge internal capacitor system 250 a to a higher voltage(V_(BURST)) above the normal high threshold voltage (V_(MAX)) to storeextra energy for a short duration high current burst such as, but notlimited to, the start-up current required by motor 310 or pump system300. An ECG signal may, for example, be used to determine when it istime to activate moving valve assembly 1300 a via motor 310. An ECGsignal is communicated to internal control system 210 a. At a point intime determined by the ECG signal, external coil 130 a charges capacitorsystem 250 a to V_(BURST). Once capacitor system 250 reaches V_(BURST),internal control system 210 a initiates start-up of motor 310. Thestart-up motor 310/movement of moving valve assembly 1300 a may be timedto occur only when V_(BURST) is achieved. Such synchronization of thestart-up current required by motor 310 or pump system 300 and V_(BURST)reduces the risk of triggering the start-up current required by motor310 or pump system 300 when the internal voltage is somewhere other thanat V_(BURST).

In a number of embodiments described herein, a spread spectrum powersignal is used advantageously as described above and operatesindependently from secondary or internal system. The power signal may,for example, be factory set to a center frequency with a fixed number ofchannels and fix frequency bandwidth. The power signal frequency may,for example, hop through the channels without knowledge of the status ofthe secondary or internal system. Additionally, the use of a spreadspectrum power signal does not need to contain data. In a number ofembodiments, the signal is for power only and contains no data. Powermay, for example, be sent via a first spread spectrum signal in a firstfrequency band, while data may be sent via a second spread spectrumsignal in a second frequency band different from the first frequencyband. In a number of embodiments, power is sent via frequency hoppingspread spectrum or FHSS and data is send via direct sequence spreadspectrum or DSSS.

In a number of embodiments, power is sent via a direct sequence spreadspectrum (DSSS) signal which phase-modulates the external controllerclock signal pseudo-randomly with a continuous string of pseudonoise(PN) code symbols called “chips”. Chips have a much shorter durationthan a clock pulse, meaning each clock pulse is modulated by a sequenceof much faster chips. Therefore, the chip bit rate is much higher thanthe clock bit rate. DSSS effectively, multiplies the clock by a “noise”signal. This noise signal is a pseudorandom sequence that has afrequency higher than that of the clock signal. The resulting signalresembles white noise. A plot of the frequency spectrum transmitted hasa roughly bell-shaped envelope centered on the carrier frequency, 122.5kHz as an example. A DSSS power transfer signal can be generated byexclusive OR-ing or multipling the clock signal from the externalcontroller 110 a with a PN code. The resulting DSSS signal is providedto the H-Bridge Driver clock pin (CLK). In some embodiments, externalsystem 100 a transmits energy without data via primary coil 130 a to theinternal system 200 a. Typically, DSSS signals are used to communicatedata. This requires the PN code to be common in the transmitter andreceivers of the signal. It also requires the PN code to have finiteduration to modulate data onto and demodulate data from the signal.Removing the data from the signal allows the DSSS signal used totransfer power to use a truly random signal with infinite duration, i.e.the PN code is never repeated. The resulting DSSS signal transfersenergy continuously across a frequency bandwidth meaning the EMIpotential from the system described herein is minimize Stated adifferent way, the system described herein simultaneously transmits afrequency envelop which contains multiple frequency components.

Another way to generate the spread spectrum signal is to use spreadspectrum clocking. A spread spectrum clock may be generated by takingthe clock and modulating it with a spreading signal such as a trianglewave signal (linear) or a Hershey kiss signal (non-linear).

In a number of embodiments described herein, a tuned primary coil isused to transfer magnetic energy wirelessly to a tuned secondary coil.The magnetic energy may, for example, be spread spectrum magneticenergy. The magnetic energy may, for example, be produced at a firstfrequency for a first time period and followed by magnetic energyproduced at a second frequency for a second time period. The magneticenergy may, for example, be produced with direct-sequence-modulatedspread spectrum with ((sin x)/x)² frequency spectrum, centered at thecarrier frequency.

In a number of embodiments, the internal system 200 a may include asecond energy storage device or system 1250 a (see FIG. 1A) in additionto first energy storage device or system 250 a (for example, capacitorsystem 250 a), which may, for example, be a rechargeable battery. Energystorage device 1250 a is not meant to power the internal system duringtypical use/operation. In typical operation (in the first state ofinternal system 200 a), all energy required by internal system 200 a istransferred from the external system 100 a. There may, however, beinstances where external system 100 a must be removed or powered down.As an example, the patient may remove external system 100 a during ashower or bath. As another example, the patient may be required to powerdown external system 100 a during air travel. Under those circumstances,internal system 200 may be placed in a second state wherein energystorage device 1250 a may take over powering internal system 200 a forshort durations. Internal system 200 a may, for example, operate at fullpower (normal operation) or may operate at a reduced power level(reduced function mode) when powered by energy storage device 1250 a.The use of energy storage device 1250 a may be limited to short durationinfrequent events, which maximize the lifetime of internal energystorage device 1250 a. This mode of operation overcomes shortcomings ofcurrently available systems and avoids the need for maintenance tointernal system 200 a every couple of years (that is, surgical removalof an aged rechargeable battery pack). When used as described herein,internal secondary energy storage device may be designed to havelifetime of seven to ten years or more. Energy storage device 1250 amay, for example, be a rechargeable Li-ion battery capable of poweringinternal system 200 a for a period of time in the range of 5 minutes totwo hours or any range therebetween (for example, in the range of 20minutes to 1 hour). In systems wherein a rechargeable battery is used topower an implanted device or system such as a blood flow assist pumpsystem continuously or at all times, a much larger battery will berequired than an internal battery used in the systems hereof. In thatregard, as internal batteries hereof are used only periodically, uponinstructions from, for example, external system 100 a, and for period oftime ranging from, for example, 5 minutes to 2 hours or any rangetherebetween, significantly smaller batteries may be used than requiredin systems using a dedicated, continuously used battery. After asituation requiring the use of energy storage device 1250, externalsystem 100 a is replaced/reactivated to resume normal operation.Additionally, energy storage device 1250 a is recharged by externalsystem 100 a. In a number of embodiments, energy storage device 1250 maybe maintained at a state of charge less than full charge to helpincrease the lifetime of energy storage device 1250 a. In that regard,deep discharges and storage or operation at full charge have a negativeimpact on battery lifetime and performance. The patient may be requiredto notify external unit 100 a that external unit 100 a will be removedor powered down. After such notification, the patient may be required towait a predetermined time to allow external unit 100 a to chargeinternal energy storage device 1250 a to full charge. As an example, aninternal Li-ion battery may be maintained at 40-50% charge state. Thepatient may, through a user interface on the external unit 100 a, notifycontrol system 110 a of external unit 100 a that external unit 100 awill be removed or powered down. The patient may be required to wait,for example, 20-30 minutes before removing or powering down externalunit 100 a to allow the internal Li-ion battery to charge to 100%capacity. Additionally, the patient may provide information to externalunit 100 a to inform of the duration of the removed or powered downevent. For short duration events, internal energy storage device 1250may not recharge to 100% capacity which minimize the required wait time.

The foregoing description and accompanying drawings set forth a numberof representative embodiments at the present time. Variousmodifications, additions and alternative designs will, of course, becomeapparent to those skilled in the art in light of the foregoing teachingswithout departing from the scope hereof, which is indicated by thefollowing claims rather than by the foregoing description. All changesand variations that fall within the meaning and range of equivalency ofthe claims are to be embraced within their scope.

1. A system, comprising: an implantable pump system adapted to assistblood flow in a patient comprising: a drive system and an energytransfer system to provide energy to the drive system, the energytransfer system comprising: an external system comprising a power sourceand an external coil, the external coil being adapted to be placed inthe vicinity of a patient's skin, and an internal system comprising aninternal coil adapted to be implanted and to receive transcutaneousenergy transmitted from the external coil, a capacitor system inoperative connection with the internal coil to be charged therefrom, thecapacitor system being adapted to store energy to provide operationalpower to the drive system, the internal system having at least a firststate wherein energy transmission from the external coil to thecapacitor system is required to provide operational power to the drivesystem.
 2. The system of claim 1 wherein the capacitor system is unableto power a reciprocating pressurizing mechanism of the drive systemthrough one stroke without energy transmission from the external coilwhen the internal system is in the first state.
 3. The system of claim 1wherein the implantable pump is adapted to be placed in seriesconnection with the aorta.
 4. The system of claim 1 wherein the internalsystem comprises no battery.
 5. The system of claim 3 wherein thecapacitor system comprises a single capacitor adapted to store energy toprovide operational power to the drive system.
 6. The system of claim 1wherein the capacitor system is capable of storing no more than 260Joules of energy.
 7. The system of claim 1 wherein the external systemcomprises an external control system in operative connection with thepower source and the external coil and the internal system comprises aninternal control system in operative connection with the first energystorage system and the internal coil.
 8. The system of claim 7 whereinin the external system further comprises an external communicationsystem in operative connection with the external control system, and theinternal system further comprises an internal communication system inoperative connection with the internal control system.
 9. The system ofclaim 8 wherein the internal communication system is adapted towirelessly transmit a signal to the external communication system toprovide information related to a voltage of the capacitor system, theexternal system being adapted to cause the power source to energize theexternal coil upon receiving information transmitted from the internalcommunication system indicating that the voltage is at least as low as alower threshold value to charge the capacitor system and to de-energizethe external coil upon receiving information transmitted from theinternal communication system indicating that the voltage is at least ashigh as a higher threshold value.
 10. The system of claim 1 wherein,when the external coil is energized, energy is transmitted from theexternal coil to the internal coil over a range of frequencies.
 11. Thesystem of claim 10 wherein, when the external coil is energized, energyis transmitted from the external coil to the internal coil in a range offrequencies under control of a spread spectrum algorithm.
 12. The systemof claim 11 wherein the nominal transmission frequency is between 50 and500 kHz. 13.-14. (canceled)
 15. The system of claim 11 wherein theexternal system and the internal system are adapted such that a changeof frequency of energy transmitted from the external coil to theinternal coil of +/−10% results in a change in transfer efficiency of nogreater than 10%. 16.-23. (canceled)
 24. The system of claim 9 whereinthe external control system is adapted to cause the power source toenergize the external coil after a determined maximum time period thatthe external coil has not been energized regardless of whether or notthe voltage is at least as low the lower threshold value.
 25. The systemof claim 9 wherein the external control system is adapted to cause thepower source to energize the external coil in a manner to result in thevoltage being greater than the higher threshold value in anticipation ofa required high energy load.
 26. The system of claim 1 wherein theexternal system comprises an external communication system and theinternal system comprises and internal communication system, wherein theexternal communication is adapted to transmit to or receiveinformational signals from the internal communication system via atleast one of an external radio or the external coil, and the internalcommunication system is adapted to transmit information signals to orreceive signals from the external communication system via at least oneof an internal radio or the internal coil.
 27. The system of claim 9wherein the external communication is adapted to transmit to or receiveinformational signals from the internal communication system via atleast one of an external radio or the external coil, and the internalcommunication system is adapted to transmit information signals to orreceive signals from the external communication system via at least oneof an internal radio or the internal coil.
 28. The system of claim 27wherein, when information signals are transmitted between the externalcoil and the internal coil, the information signals are transmittedwithin a frequency range different from a frequency range at whichenergy is transmitted from the external coil to the internal coil. 29.The system of claim 26 wherein the internal communication system isadapted to transmit a periodic status signal to confirm operability ofat least a portion of the internal system.
 30. The system of claim 8further comprising a monitoring system to measure a variable related tocurrent draw by the external coil to provide information to the patientregarding position of the external coil relative to the internal coilbased at least in part on the measured variable related to current drawon the external coil.
 31. The system of claim 30 wherein the monitoringsystem to measure a variable related to current draw on the externalcoil comprises a current sensor in electrical connection with theexternal coil and in communicative connection with the external controlsystem.
 32. The system of claim 1 wherein the internal system furthercomprises a second energy storage system, and the internal system has asecond state wherein energy is drawn from the second energy storagesystem to provide energy to the drive system.
 33. The system of claim 32wherein the second energy storage system stores sufficient energy toprovide operation power to the drive system without transfer of energyfrom the external coil.
 34. The system of claim 33 wherein the secondenergy storage system comprises an internal rechargeable battery. 35.The system of claim 34 wherein the internal system is placed in thesecond state upon instructional information being transmitted from theexternal control system via the external communication system to theinternal control system via the internal communication system.
 36. Thesystem of claim 35 wherein the external system is adapted to allow thepatient to manually cause the internal system to be in the second state.37. The system of claim 34 wherein no energy is drawn from therechargeable battery to provide energy to the drive system in the firststate.
 38. The system of claim 37 wherein the rechargeable battery isadapted to power the drive system for a period of time in the range of 5minutes to 2 hours.
 39. The system of claim 1 wherein the power sourceconsists of a single rechargeable battery pack.
 40. The system of claim39 wherein the battery pack comprises a plurality of lithium ion batterycells.
 41. The system of claim 1 wherein the external coil is energizedat a voltage of sufficient amplitude to provide an efficiency of atleast 75%. 42-53. (canceled)
 54. A method of assisting blood flow in apatient, comprising: placing an implantable pump system in fluidconnection with a blood vessel of a patient, the implantable pump systemcomprising a drive system; providing an external system comprising apower source and an external coil adapted to be placed in the vicinityof the patient's skin; providing an internal system comprising aninternal coil adapted to be implanted and to receive transcutaneousenergy transmitted from the external coil and a capacitor system inoperative connection with the internal coil to be charged therefrom, thecapacitor system adapted to store energy to provide operational power tothe drive system; and operating the internal system in a first statewherein energy transmission from the external coil to the capacitorsystem is required to provide operational power to the drive system.55.-56. (canceled)